Before the 2014 Russian annexation of Crimea, North Atlantic Treaty Organization (NATO) countries bordering Russia warned of potential Russian aggression in the region. In response, NATO deployed forces to the Baltics and Poland. At the same time, despite this reassurance, the most directly-threatened nations pursued two options to increase their deterrent and response capacity as an element of their Comprehensive Defence — the whole-of-society capacity for national defence. The first option focused on increasing the number of Ministry of Defence (MOD) Territorial Defence Forces (TDF), also known by other terms, such as the Home Guard (NSHQ, 2020, pp. 37-39), which is responsible for defence of the nation’s territory in conjunction with conventional forces in wartime and civil defence during peacetime. TDFs are cost-effective and quickly bolster the nation’s traditional, active-duty military forces where ‘political will or budget’ constrains the growth of the active force (Klisz, 2020, pp. 2-3). Additionally, the TDFs are intended to transition into guerrilla or partisan forces, which can employ irregular hit-and-run tactics in-extremis during resistance to invasion or occupation. NATO refers to these forces as an adapted force in recognition that it is ‘a combination of the traditional armed forces and predesignated elements of society’ (NSHQ, 2020, p. 46). The second option focuses on developing a government-led national underground resistance organisation before a crisis (Fiala, 2020, p. 1). A national underground resistance organisation is a specially developed, organised, and trained group of individuals, sanctioned by the government to operate clandestinely with the goal of maintaining continuity of governance and resisting an occupier through both violent and non-violent means. Both options focus entirely on the nation’s territorial defence in hopes of changing the strategic decision-making of a potential invader or occupier first to bolster deterrence, but if deterrents fail, to conduct resistance to invasion and occupation (Klisz, 2020, p. 5).

Interestingly, both options have historically been combined when nations found themselves under occupation. The difference here is the fact that both elements have designated roles and are trained and organised for these roles prior to a crisis, instead of the historic norms of forming in-extremis after an invasion or occupation has happened. For convenience of understanding, one should consider the composition of resistance organisations to have two separate elements, or wings, military and civilian, while acknowledging that they are rarely mutually exclusive in practice. The military wing of resistance to invasion or occupation is a role historically best suited for the TDF. In European history, including in the recent past, guerrillas or partisans have played a significant role in resistance due to the largely rural terrain found in the theatre. Rural terrain favours this kind of force, allowing units of significant size to move undetected, conduct guerrilla or partisan actions — such as raids or ambushes — and then quickly escape. However, resistance organizations in urban areas like Paris and Warsaw during WWII needed to adapt into clandestine cells and networks, also known as urban guerrillas, to help manage the organisation’s signature and decrease the chance of interception by the occupying forces (Korbonski, 2004, pp. 10-11). With increased urbanisation, this trend will continue. The civilian wing of the resistance is predominantly clandestinely organised through cells and networks in both urban and rural environments, consisting of two parts: the underground and the auxiliary. The underground element contains the full-time clandestine resistance members, including of the shadow government, and provides significant capabilities to support the entire resistance, including clandestine governance, administrative support, command, control, integration of armed and non-violent actions, intelligence collection, counterintelligence, sabotage, subversion, and logistics. The underground is the most critical element of the entire resistance organisation, the destruction of which Roger Trinquier called the masterstroke of modern warfare (1961, pp. 8-9). The second part of the civilian wing is the auxiliary, which operates clandestinely as well. However, the auxiliary members are part-time resistance members only, using their daily lives and livelihoods as cover for their clandestine activities that support the resistance. Historically, the civilian wing of the resistance organisation is larger than the military wing, like the tooth-to-tail ratio of a military organisation; it is organisational behaviour that happens naturally based on organisational requirements and various environmental factors, such as the human and physical terrain, instead of being planned. (Jones, 2012, pp. 5-6).

The Ukrainian response to Russia’s 2022 invasion provides modern proof of the potential of these elements armed with modern weapons. The Ukrainian government hastily organised and armed civilians as irregular members of the TDF immediately before or during the invasion to increase the capacity of the nation to disrupt the Russian invasion. To date, the Ukrainian resistance to invasion has been surprisingly successful. However, there is potential that the resistance to invasion could still fail, resulting in a Russian occupation of a part or whole of the country. Should this occur, the resistance’s main effort should focus on resistance to occupation (Jones, 2022b). Based on new laws, the Ukrainian special operations forces (SOF) have the lead in organising and developing the underground resistance to occupation (LoU, 2021). The concern is that resistance to invasion is significantly different from resistance to occupation, and the latter is more challenging to set up even in peacetime (Jones, 2022b). Without a clear understanding of the differences, countries may inadvertently learn the wrong lessons from 2022 Ukraine.

There is a vast amount of literature on guerrillas and partisans relevant to the application of TDF in resistance to invasion scenarios. However, very little has been published regarding the integration of clandestine TDF as a critical part of the military wing of an underground resistance organisation focused on resistance to occupation, which is the primary subject of this study. The Polish Home Army as the military wing of the Polish Underground State during WWII and the subsequent Polish Independence Underground through 1963, a multi-dimensional case study that spans several decades and two different brutal occupiers, serves as the basis for analysis for this research. Based on this analysis, three critical lessons emerge for the integration of the underground resistance organisation and the TDF as a critical component of its military wing for nations developing pre-crisis resistance organisations: 1) the criticality of civilian control, 2) ambiguity, protractedness, and the TDF, and 3) scaling the TDF and underground. Lastly, recommendations are provided to support the implementation of these lessons learned.

The last Polish partisan killed in action was Jósef Franczak, known by his pseudonym ‘Laluś’, in the fall of 1963. His death marked the end of the prolonged effort of the Polish armed resistance to regain their independence from three inhumanely brutal back-to-back occupations — Nazi Germany and the Soviet Union, 1939-1941; Nazi Germany, 1941-1944; and then the Soviets from 1994 onward (Musiał, 2016, para. 21). This long struggle began in the fall of 1939 when Nazi Germany and the Soviet Union invaded and occupied Poland. These events set in motion fifty years of occupation, during which the Polish people faced unspeakable brutality, genocide, and deportations. Due to their incredible resilience and perseverance, the nation survived and successfully transitioned into a free and open democracy in the fall of 1989.

The resistance began immediately after the Nazi invasion and subsequent occupation in 1939 — with both military and civilian leaders organising clandestine cells and networks. What started as the Service for Poland’s Victory grew into the largest organised underground of World War II, the civilian-led Polish Underground State, which would reach a strength at its height of over 380,000 clandestine members (Koskordan, 2009, p. 63; Bór-Komorowski, 2011, p. 25). Critical to the establishment of the Polish Underground was the legitimacy it enjoyed being nested under the government-in-exile based on the 1935 constitution. This nesting ensured the legal continuation of an independent Poland under both Polish domestic law and international law (Korkuć, 2019, p. 34). The underground state included the shadow government — the Government Delegation for Poland, with its clandestine parliament of the various political parties — the Council for National Unity (Bór-Komorowski, 2011, p. 169). The organisation of the underground state effectively linked the government-in-exile, underground administration, and armed groups down to the municipal level and members of every class and profession (Bór-Komorowski, 2011, p. 42). The underground military effort coalesced into the Union of Armed Struggle (Bór-Komorowski, 2011, p. 28), transitioning in 1942 to its most famous name, the Home Army (Armia Krajowa), which combined all military organisations that answered to the Polish authorities in exile (Bór-Komorowski, 2011, p. 69).

After the invasion and subsequent Nazi and Soviet occupation of Poland in 1939, the remnants of the Polish military faced three options: 1) withdrawal to friendly territories to fight another day—ideally, as part of an allied liberation force to free Poland, 2) continuation the armed struggle as uniformed guerrilla fighters or partisans from rural areas of Poland, or 3) discarding their uniforms and attempting to melt back into the urban populations in order to continue the fight as members of the underground resistance (Koskodan, 2009, p. 9). The latter was the most difficult for the remnants due to their association with the military being known to the occupiers, and therefore, they could not return to their former lives. As a result, they had to take extraordinary steps to hide their former selves by assuming new identities either by acquiring identity documents of those deceased or killed during the conflict or through underground forgery (Koskodan, 2009, p. 62; Bór-Komorowski, 2011, pp. 18, 25, and 36). At the strategic level, the Polish government-in-exile envisioned gaining a place of influence on the ‘Anglo-French Supreme War Council’ to influence its decision related to Poland based on the contributions to the war effort by the free Polish armed forces and the resistance in Poland (Kochanski, 2012, p. 204).

With the establishment of the Home Army, one of the critical functions was to have an armed military force large enough to support a future national uprising, code-named Operation Tempest, which was ideally in support of an Allied liberation operation. Building an armed military of this size required hundreds of thousands of members to hide their arms and themselves until directly before the uprising to ensure that it was both viable and effective. While most of the Home Army was in hiding, specialised units were organised and utilised for targeted armed actions. The forest partisans participated in continuous sabotage efforts across the occupied areas and general retribution and guerrilla attacks against the Germans (Koskodan, 2009, pp. 186-187). The Directorate of Diversion, or Kedyw, was a specialised battalion for sabotage, subversion, and other special operations (Bór-Komorowski, 2011, p. 170). Lastly, the government-in-exile’s intelligence organisation, the Sixth Bureau, developed a close relationship with the British Special Operations Execute (SOE) Polish Section, resulting in 605 Polish special operations personnel called Chichociemni trained in SOE underground skills (Kochanski, 2012, p. 286; Fuegner, 2014, pp. 93-94). A total of 316 Chichociemni ultimately returned to providing liaison, training, conducting subversion and sabotage, and delivering 300 tons of equipment and supplies to support the Home Army (Fuegner, 2014, pp. 93-94; Koskodan, 2009, pp. 190-191).

Unbeknownst to the Polish government-in-exile, during the 1942 Tehran Conference, the US President and British Prime Minister agreed to allow Poland to be apportioned to the Soviet sphere of influence at the end of the war’s end to ensure its continued efforts to defeat Germany. From 1943 onward, the Polish government was slowly delegitimised as the Soviets began to have success against the Germans. The Soviets began setting the stage in 1941 for establishing a pro-Soviet political infrastructure in Poland, using Polish communists in Russia to re-establish the Polish communist party. This group was inserted into occupied Poland and established as the Polish Workers’ Party in 1943, laying the groundwork for the Soviet plan. The Soviet replacement for the Polish government, the Union of Polish Patriots, was then created in Moscow, followed by the establishment of a new Polish Army (Kochanski, 2012, pp. 372-377).

In 1944, with the German defeat seemingly imminent, the leaders of the underground state decided to execute a modified Operation Tempest, with the main effort now being a mass uprising in Warsaw. Warsaw was intentionally excluded from the original plan to protect it from destruction prior to this decision (Richie, 2013, pp. 163-164). The change would ensure the Home Army liberated the city from the Germans, not the Soviets, hoping this would change decisions made during the Tehran Conference (Bór-Komorowski, 2011, p. 170; Richie, 2013, pp. 163-164; and Kochanski, 2012, pp. 398-402). While the Polish government-in-exile approved the plan, there were apprehensions that an uprising would expose the entire underground organisation to the Soviets (Richie, 2013, pp. 199-207). While the Warsaw Uprising was the seminal event of the Polish Home Army, its detailed description is beyond this study. Suffice it to say that the Home Army proved their fighting spirit, even gaining the respect of the Germans, but it did not change the Allies’ prior decisions as hoped (Koskodan, 2009, p. 220). However, the Soviets did use the German anti-uprising operations as a proxy to destroy the underground’s capacity for future resistance, which it effectively did due to the mass exposure of the underground as it transitioned from a clandestine to an overt force. The Soviets understood that allowing the underground state to remain intact would threaten their occupation. Once the Germans had set the stage, the Soviets were able to hunt down many of the underground remnants, having prepared for such an event since 1939. Even at that early stage, the Soviet NKVD or People's Commissariat for Internal Affairs had begun its efforts to penetrate the Polish Underground when the Soviets occupied eastern portions of Poland, continuing throughout the war. The NKVD proved much more adept at counter-resistance operations than their German counterpart, systematically identifying, arresting, and eliminating the remaining underground leaders (Karski, 2013, p. 98).

The Soviets quickly established the initial Soviet-puppet administration, the Polish Committee of National Liberation, known as the Lublin Committee, charged with administering the Polish territories until a provisional government could be established (Kochanski, 2012, p. 386). Despite protest from the Polish Government-in-exile, the Polish Provisional Government was established and immediately recognised by the Western allies, ending the government-in-exile and the underground states’ government (Korbonski, 2004, p. 423 and pp. 444-453; Kochanski, 2012, pp. 536-537). The Council of National Unity, the civilian shadow government oversight body, decided to disband the underground (Korbonski, 2004, pp. 442-449). In its final order, the civilian oversight called for continued ‘perseverance in the attitude (authors’ emphasis) of resistance’ but also called for the armed resistance to end, noting,

Do not let yourselves be provoked into an armed struggle. It could not now bring any advantage to the aims for which we are striving, but would expose ardent, and often most valuable individuals to doom…. Your remaining in the forests has already become the cause for a bloody pacification campaign. You are doomed to perish there. (Korbonski, 2004, pp. 448-449).

This last directive was disregarded by many who aspired to re-establish a nationwide underground and armed elements who continued their struggle in nearly every province in Poland (INR, 2007, pp. XLVII). To carry on the resistance against Soviet occupation, the remnants of the underground state established a new underground organisation, Independence (Niepodległość). It immediately suffered setbacks due to the proficiency of the NKVD (Kochanski, 2012, p. 524). These initial failures foretold a problematic future for armed resistance under Soviet rule. From 1945 to 1947, the NKVD continued to master their counter-resistance operations employing penetrations, agent provocateurs, pseudo-operations (e.g., using former partisans to contact and expose active units), anti-partisan search and destroy operations, filtration camps to screen citizens for political loyalty, and amnesty programs to gain insight into the remaining clandestine elements (INR, 2007, pp. XLVI-XLVIX). Over 75,000 underground members were exposed by late 1947, including the elimination of the last national underground organisation and the last ‘supra-regional’ organisation in 1948 (INR, 2007, pp. XLVI-XLVIX; INR, 2007, pp. L). Only a few thousand-armed resistance members remained in hiding by 1963 and hunting them down was only a matter of time.

Three key lessons emerge from the case study explicitly relating to TDF integration into the underground resistance organisation that have not yet been addressed in research or, if so, only minimally, yet are critical for countries considering this integration problem for the future. The three lessons are 1) the criticality of civilian control, 2) ambiguity, protractedness, and the TDF, and 3) scaling the TDF and underground. These lessons are only generally framed with the goal that they provide a foundation for further research and analysis.

Historically, such as in the case of the Polish resistance, the military and civilian resistance components coalesce naturally. The Polish resistance was different in the fact that the civilian component and its lead role were legitimised constitutionally, setting up robust civilian control from the beginning of the German occupation in 1939. The importance of this aspect is apparent when compared to the lack of civilian leadership upon Soviet occupation in 1944, resulting in disparate armed resistance with no legitimate government, which ultimately failed. It is the WWII period of the Polish resistance that provides nations developing organised resistance capabilities today with a unique and applicable model. The first and most important aspect of the Polish Underground for modern-day application is the clear linkage from the constitution to the government-in-exile to the organised and civilian-led underground and shadow government with its subordinated military arm, the Home Army. Therefore, like the Home Army, a TDF integrated into the future underground resistance organisations will enjoy its most significant legitimacy when it has civilian oversight, control, and international recognition. The civilian oversight, control, and resultant legitimacy should be easily traced to the foundational legal documents, such as the constitution. Civilian oversight ensures that civilian-military efforts have unity of effort and unity of control. As Jon Rahbek-Clemmensen (2013) astutely notes,

The need for civilian control grows out of the accountability principle that defines modern society. Simply put, ensuring that political leaders control the military is part of the social contract. However, civilian control becomes difficult because of the structural relationship between the government and the armed forces. The military has its own preferences and it can use its access to information conduits to pursue policy goals that differ from those favoured by the government (p. 127).

Legitimised governance structures — exiled and shadow governments — are critical to the national acceptance of these efforts as demonstrated by the Polish Underground. As a former Polish Speaker of the House and an original organiser of the Polish Underground noted, ‘The underground movement, like the Government in exile, must be based on democratic ideals’ (Korbonski, 2004, p. 10). The Commander of the Union for Armed Struggle further supported this required legitimacy by envisioning the ‘forming of the military organisation on a wide national front…and calling into being of a supreme conspiratorial political body’ (Korbonski, 2004, p. 24). Both ensured that the military efforts of the resistance remained nested within the legitimate Polish geopolitical objectives. The continuity of governance ensured the civilian control and legitimacy of the resistance from the start, providing a model for contemporary efforts to organise resistance.

While civilian control is not new to the modern Western militaries and is discussed generally in both the Resistance Operating Concept (Fiala, 2020, pp. 9-12) and the Comprehensive Defence Handbook (NSHQ, 2020, pp. 89-90), the case study demonstrates a need for significant additional research in this area. One of the difficulties for countries developing organised resistance capabilities today is the inherent militarisation of these efforts. Over the last ten years, the MOD, more specifically SOF, has primarily served as the lead element for the whole-of-nation organised resistance efforts (Jones, 2022c). Although not intentional, this military-in-the-lead trend has resulted in SOF and the TDF or their equivalents being viewed as the primary resistance component, with little thought being given to the shadow government or the underground. This is further complicated by the fact that the development of these civilian-led elements is not well understood by either military or civilian government leaders. These factors unintentionally lead to a problematic reduction in the role of civilian control in these efforts, which is counter to the lessons of the Polish Underground.

In other words, instead of the military in the lead, the lead element should be specially identified government civilians, the future shadow government, which is tasked with developing the nation’s organised resistance, including framing the legal and organisational principles to be codified by legislative action, and the roles and responsibilities of the rest of the government and society. The civilians in the lead would then delegate portions of the planning and organisation to the various ministries, departments, or other agencies, including the MOD, as required to fully develop their portions of the resistance organisations. The military’s role should be focused on the integration of armed resistance into the overall resistance to invasion and resistance to occupation plans. While the MOD would likely remain in the lead for resistance to invasion as a transition from the conventional defence to potential occupation, civilian control should take place immediately prior to or at the onset of the occupation in order to ensure continuity of governance, which is a political activity that sets the stage for a legitimate resistance to occupation.

Legally established civilian control also allows the shadow government to control the legitimate use of violence against an occupier, which increases the legitimacy of underground and government-in-exile, and dissuading behaviours like vigilantism and militantism by the population. Ultimately, it ensures that the government controls who is recognised as belligerent for legal purposes. This is critical given the increased trends of contemporary conflicts that may include local militias and foreign fighters that have political or ideological leanings that could ultimately discredit the underground resistance organisation’s efforts. Foreign fighters present a unique challenge for the shadow government and government-in-exile, particularly regarding how the underground state controls the foreign fighter influx into a zone of conflict and how it mitigates the risk of unaligned, untested, and unvetted foreign fighters that the occupier can use to discredit the resistance. This is not a new concern; the Polish Underground faced the same problem, as General Bór-Komorowski (2011) explained,

We had to make the Germans feel that they were dealing with a military organisation which permeated every section of national life and was directed by a centralised single command. They had to understand that they were not faced with gangs of bandits or several [uncoordinated] groups (p. 170).

Per the legal frameworks for national resistance the roles and responsibilities of the resistance, individuals are either part of the resistance organisation or are directed not to participate in armed resistance to protect them from the occupier. They may, however, be encouraged to support shadow-government directed, non-violent resistance efforts and passive resistance as designated by the shadow government.

Finally, broad international recognition of the Polish government-in-exile and the national resistance was also a critical factor that rested solely on legitimate civilian control. It could have turned the tide for Poland if they had successfully changed the Tehran Conference decisions. The goal is to ensure that nations maintain their governance and have contingency plans in place (Korkuć, 2019, p. 34). While the Allies recognized the exiled government with support in the early years of WWII, Allied support quickly dropped in favour of the puppet government installed by the Soviets after they occupied Poland. This juxtaposition of these events illustrates the power of international recognition and legitimacy. Ultimately, civilian control increases the relative power of resistance to occupation and its pursuit of the political goal to re-establish the legitimate government once the occupier is defeated. The political goal must always remain the central focus, and as a result, it requires civilian leadership and oversight from the beginning of the effort to organise the resistance prior to a crisis. The resistance — violent, non-violent, or both — is simply the means to achieve the political goal when all other defence options have failed.

The second lesson is understanding the operational art of clandestine organisations — maintaining ambiguity to protract the conflict as long as needed to defeat the occupier — and the implications for the TDF (Jones, 2021a). This concept, referred to as ambiguity and protractedness, is the quintessential theory that guides all clandestine organisations on their singular path to survive long enough to achieve their goal – in other words, to ‘win by not losing’ (Jones, 2017, pp. 1-2; Jones, 2012, pp. 61-65 and p. 71; Metz and Millen, 2005, p. 15). Losing means the destruction of the clandestine organisation and the elimination of its members — through arrest, death, or amnesty — before the desired political outcome is achieved (Jones, 2022a). Ambiguity is the intentional effort by the clandestine organisation to deny the occupier the ability to detect, engage, or destroy the members of the organisation (Jones, 2022a; Jones, 2017, p. 1). Intentional efforts include organisational compartmentalisation (form) to limit damage to the network if interdicted and clandestine tradecraft (function) to keep the signature of the clandestine members, their association with each other, the organisation, and their activities hidden (Jones, 2017, p. 4). Protractedness is the intentional extension of the resistance in time or space through ambiguity to defeat the occupier unilaterally through either morale exhaustion or military action by external forces (Jones, 2022a; Jones, 2017, p. 1). The duration of these two options likely differs — as the Polish experience from 1945 to 1990 shows, unilateral resistance to achieve exhaustion can take decades rather months or years depending on the decision-making and mobilisation timelines of allies or partners (e.g., a NATO Article 5 response). Three insights emerge from a comparison of the above to the case study: 1) The risks to ambiguity due to transitions from overt to clandestine TDF, 2) The need for organisational and operational ambiguity of clandestine TDF units, and 3) The need to modulate operational ambiguity to achieve protracted operational effects.

First, the overt TDF cannot simply transition to a clandestine one, such as transitioning from resistance to invasion to occupation. This idea runs contrary to historical and current employment concepts, which stipulate that these forces can support civil defence, conventional forces, and conduct guerrilla warfare, clearly showing that little thought has been given to the risk of these concepts (Veebel et al., 2020, p. 21). Ambiguity requires both clandestine forms and functions, neither of which neither current nor historic TDF or adapted force operational concepts address. Participating in overt actions results in individual and organisational exposure. Future occupying forces will actively seek to correlate their identity, roles, social networks, skills, and operational and digital signatures with resistance activities, allowing adversaries to identify them as a trackable person of interest before or during the occupation. Additionally, publicly available rosters, records, and media coverage provide the starting point for interdiction. None of the above should be surprising, as the same information and processes are used to collect, correlate, and target individuals by most military, intelligence, or law enforcement organisations that have operated against insurgent, terrorist, or criminal networks. Therefore, transitioning the TDF from overt to clandestine is high risk and requires extraordinary efforts to do so successfully, such as providing transitioning TDF members with new identities as was done in WWII. Nevertheless, successfully providing new identities today is much more difficult given the occupier’s likely use of technology.

Second, as the case study showed, the Home Army successfully developed a clandestine organisation to hide its forces leading up to the uprising. However, this required former military members to gain ambiguity by changing their identities (Koskodan, 2009, p. 62; Bór-Komorowski, 2011, pp. 18, 25, and 36). Therefore, developing a dedicated clandestine TDF would reduce the risks and incorporate clandestine form and function. A cellular structure describes this organisation's clandestine form, where the building blocks are clandestine cells and networks of trusted individuals (Jones, 2012, pp. 12-30). In this case, the clandestine TDF structure must apply the principles to ensure survival, which may mean a transformation from hierarchical military structures to networked structures that apply clandestine safeguards to achieve an ambiguous form. To maintain their ambiguity, individual members execute signature-minimizing acts as they undertake operations, contact with one another — directly and indirectly — through various methods, including digital, and go about their daily lives. They do this using clandestine tradecraft for personal communications, detecting and countering surveillance, re-establishing the cell or network after the removal of a critical leader, teaching how to recruit, safeguarding locations, and facilitating training, all to maintain ambiguity (Jones, 2012, pp. 39-59). The clandestine TDF members require additional training in the various techniques described and practice them ideally in training and in their daily lives before a conflict, so these techniques become second nature. Ideally, members of the clandestine TDF would practice clandestine tradecraft to keep from being known or detected by the occupier, thus denying useful information that would otherwise orient the occupier’s targeting process. This includes ensuring the security of personal information and information associating members to the organisation or each other to deny this information to the occupier, the exposure of which could be catastrophic (Jones, 2022b).

Lastly, ambiguity and protractedness also apply to operational signatures. Like the Home Army, the TDF would likely consist of clandestine elements waiting for an uprising and other specialized units to maintain pressure on the occupier through raids, ambushes, sabotage, or subversion. The specialised units would have the most visible signature due to their inherent nature. Historically, the resistance’s goal is to never get decisively engaged to live in order to fight another day, a subset of the ‘win by not losing’ concept. That concept does not change with ambiguity and protractedness; the key to long-term protractedness is that the resistance continues to interdict, degrade, and disrupt the occupier to keep it off-balance, but these operations never result in a decisive action by the occupier to destroy or defeat the resistance. Ultimately, the resistance must be viable for as long as needed to achieve the political end state. Defeat prior to this due to having a high signature and having the occupier conduct decisive operations against the entire organisation would be self-defeating. The goal is for the specialised TDF units to be a continual annoyance, causing the occupier to waste resources and time, but never in a way to allow the occupier to counter the TDF actions decisively. Constant pressure, below a threshold that would result in decisive operations against the resistance, is the foundation for the exhaustion of the occupier. This pressure does not have to be kinetic or lethal; it should be a mixture of violent and non-violent actions, subversion, and sabotage, partially or fully supported by the full range of information operations.

The final lesson is scaling, in other words, determining the total size of a resistance organisation in comparison to the occupiers, including both the military and civilian members. There are no doctrinal methodologies for determining the scale of resistance organisations as part of pre-crisis development other than general and largely unhelpful concepts, such as those outlined in the 2020 Resistance Operating Concept which states, ‘The political, physical, socio-cultural, and other landscapes will determine the size, shape, activities, and scope of the resistance’ (Fiala, p. 13). This leads countries to develop pre-crisis resistance capacity structures based largely on budgetary or manpower constraints instead of scaling the resistance organisation based on a specific invasion or occupation threat (Jones, 2022c). Nations developing TDFs face two TDF scaling issues for resistance based on ambiguity and protractedness lessons learned — the need for an overt TDF to support resistance to invasion and for a clandestine TDF to support resistance to occupation as part of the military wing of the underground resistance organisation. For resistance to invasion, the scale is simpler to calculate, as it is based on a gap analysis between the total conventional military manpower available to a country and the required manpower to defeat an invader based on the correlation of forces for the projected invasion force. This correlation of forces could be as simple as the generally accepted one-to-three ratio of a nation’s defensive capabilities to the invasion force. The proper clandestine TDF scale for resistance to occupation is more complex due to numerous factors, such as the country’s ratio of rural to urban areas, which increases or decreases the operating spaces for guerrillas or urban clandestine networks. Historically, however, it is generally accepted that the resistance has a higher potential to win when there are less than ten occupying force personnel for each resistance member (Connable and Libicki, 2010, p. 127). While not perfect, understanding the ten-to-one force ratio gives nations developing pre-crisis resilience a starting point to properly scale their efforts to ensure the ratios are in their favour. The key to determining scale is the analysis of the potential occupation force. Once this is determined, then the appropriate minimal scale of the resistance organisation can be determined to achieve a better than ten-to-one ratio. The goal is to increase the resistance strength sufficiently to ensure the greatest chance for the resistance to occupation to succeed. This necessity is then balanced with the budget and force structure constraints of the nation developing pre-crisis resistance capabilities, which in turn helps the national-level decision-makers determine investments in the overt TDF for resistance to invasion to compliment the conventional capabilities and the clandestine TDF to support armed resistance to occupation requirements.

The following two examples explain this concept in more practical terms, one based on the case study, and the other on the 2022 Russian invasion of Ukraine. First, with over 380,000 members, the Polish Underground was an example of the kind of scale these endeavours require. Using the 10:1 ratio, the Polish Underground could have challenged up to 3.8 million occupation forces. For the purposes of this study, if we assume the 380,000 Polish Underground members were organised prior to the invasion, then the correlation of forces given approximately 2.2 million German and Soviet forces in Poland during the initial occupation against the resistance would be 6:1 in favour of the resistance (Korkuć, 2019, p. 26 and p. 29). This may explain the long-term Polish Underground successes against the German occupation — successes meaning the ability to maintain both a viable underground organisation and continued pressure on the occupier from 1939 to 1944, ultimately mounting a large-scale uprising in 1944. It also explains the failure after 1944 due to the Underground’s exposure to the Soviets during the uprising in addition to the NKVD penetrations in WWII, and the NKVD operations through 1963, which continually decreased the number of resistance members. Ultimately, these events led to a reversal in the force ratios and the ultimate destruction of the Polish resistance over time. Second, the 2022 Russian invasion of Ukraine provides a modern example, where the invading force consisted of approximately 150,000 troops. Assuming the unlikely worst-case scenario that all 150,000 troops would make up the occupation force, the Ukrainian resistance to occupation would need to have at least 15,000 members, with more increasing the probability of success for the resistance. Refinements in the scale could be made based on the likely attrition rates of the invader due to both conventional defence and the TDF resistance to invasion efforts, as well as the known counter-resistance doctrine and capabilities of the occupier. As the Polish Underground discovered, the Soviets were much better at counter-resistance operations compared to the Germans for example. One additional consideration for nations with bilateral or multilateral defence agreements, such as NATO allies, is the fact that these additional capabilities would further challenge the occupier’s correlation of forces. Assuming that partners or allies would require time to build enough combat power to conduct a liberation operation to restore the occupied nation’s territorial integrity, the resistance would have to maintain its capacity to resist for an extended period, from months to potentially years. Once the partners or allies are ready, the occupier could be confronted simultaneously with a national uprising and a liberation operation. For nations without any defence agreements, the resistance would be the only means of defeating the occupier, which could take years to decades as in the case of Poland. The resilience of the resistance organisation for the non-aligned nation would require potentially greater resistance capacity.

Once the overall scale of the underground resistance organisation is determined, then the ratio of the military to civilian components of the organisation can be determined. These ratios can fluctuate from one to three military to civilian resistance members to one to nine, the difference being heavily influenced by the urban and rural terrain ratios and the amount of auxiliary support available (Jones, 2012, pp. 5-6, 30). Ultimately, scaling the resistance organization and its military component, consisting primarily of the integrated TDF, sets conditions for the overall success of the resistance to occupation. Scale combined with ambiguity and protractedness and civil control provide the key elements for nations to successfully organise resistance prior to the conflict.

This study focused on the unique characteristics of integrating the historically overt TDF with the clandestine underground resistance organisation as part of efforts by various countries to build national resistance capacities prior to a conflict. It provided the theoretical and historical underpinnings of the concept of TDF and underground integration, including observations from the 2022 Russian invasion of Ukraine. To better understand the unique aspects of TDF and underground integration, this study used the case study of the Polish Home Army’s integration into the Polish Underground State in WWII under German occupation and the Polish Independent Underground until 1963 under the subsequent Soviet occupation. This prolonged case study, with two brutal but distinctly different occupiers, provided a unique perspective of developing large, civilian-led organized underground resistance organisation with a TDF-equivalent largely clandestine military wing, and applicable lessons learned to modern efforts to develop national underground resistance organisations prior to a crisis.

Based on the case study analysis, three key lessons were identified and discussed: 1) the criticality of civilian control, 2) ambiguity, protractedness, and the TDF, and 3) scaling the TDF and underground. While the need of civilian control is not new to the military, the Polish Underground case study highlights the relevance and extent of civilian control in a big organized national resistance organization, as well as its impact on the whole effort's legitimacy. The second lesson addresses the application of clandestine operational art by the underground resistance organisation, including its military wing, to achieve ambiguity — remaining hidden from the occupier with the goal of protracting the conflict until the political goal of the resistance is achieved, the defeat of the occupier and restoration of governance and territorial integrity. The concept of ambiguity is totally new to the historically overt application of the TDF as guerrillas or partisans but is much more in line with the lessons of the Polish Home Army as the clandestine military wing of the Polish Underground State. The final lesson, properly scaling the TDF and underground to achieve the political goals of defeating the occupier, is a topic that has not been well researched in terms of developing pre-crisis resistance organizations, but this study outlines the general concept of scale, additional considerations, and military-to-civilian ratios.

Eight recommendations are offered to nations developing pre-crisis resistance capabilities to implement the TDF and underground lessons learned:

Although the lessons and recommendations outlined in this study focus on integrating military and civilian capabilities into underground resistance organizations in support of pre-crisis national resistance efforts, they can be similarly applied across every ministry, department, or agency of the nations developing pre-crisis resistance capabilities and may aid in successful implementation. No single organisation can effectively establish a viable national resistance organisation in a vacuum. It must be a whole-of-government effort, legitimised through legislation, civilian-led, with ambiguity and protractedness as the guiding principle from the start, and scaled correctly to deter, and if necessary, to defeat an invasion or occupation