The Underground State was perceived by supporters as a legal continuation of the pre-war Republic of Poland (and its institutions) that waged an armed struggle against the country's occupying powers: Nazi Germany and the Soviet Union.

The Underground State encompassed not only military resistance, one of the largest in the world,[b] but also civilian structures, such as justice, education, culture and social services.

The influence of the communists eventually declined amid military reversals (most notably, the failure of the Warsaw Uprising) and the growing hostility of the USSR.

During the Soviet-backed communist takeover of Poland at the end of the war, many Underground State members were prosecuted as alleged traitors and died in captivity.

Abandoned by the Western Allies, finding it impossible to negotiate with the Soviets, and wishing to avoid a civil war, the key institutions of the Underground State dissolved themselves in the first half of 1945.

[3][4] SZP founder General Michał Karaszewicz-Tokarzewski received orders from Polish Commander-in-Chief Marshal Edward Rydz-Śmigły to organize and carry out the struggle in occupied Poland.

[13] Given that the ZWZ focused on military aspects of the struggle, its civilian dimension was less clearly defined and developed more slowly—a situation exacerbated by the complex political discussions that were then unfolding between politicians in occupied Poland and the government in exile (first located in Paris, and after the fall of France, in London).

[9][18][19] The National Council (Rada Narodowa) was formed by the government in exile in December 1939, including representatives from different Polish political factions.

[9] Meanwhile, in occupied Poland, a major step toward the development of the organization's civilian structure was taken in late February 1940, when the ZWZ established its local version of the National Council, the Political Consultative Committee (Polityczny Komitet Porozumiewawczy, PKP).

[31] By 1943, the PKP had evolved into the Home Political Representation (Krajowa Reprezentacja Polityczna, KRP), which served as the basis of the Council of National Unity (Rada Jedności Narodowej, RJN), created on 9 January 1944.

[33] Meanwhile, the military arm of the Underground State expanded dramatically, and the ZWZ was transformed into Armia Krajowa (AK, or the Home Army) in 1942.

[35] In August 1943 and March 1944, the Polish Underground State announced its long-term plan, which was partly designed to undercut the attractiveness of some of the communists' proposals.

[33][40] The plan promised land reform, nationalization of the industrial base, demands for territorial compensation from Germany, and re-establishment of the country's pre-1939 eastern border.

[36] According to the plan, the country's Eastern borders, as delineated by the 1921 Treaty of Riga, would be kept while in the north and west compensation would be sought from German territories.

[39] Thus, the main differences between the Underground State and the communists, in terms of politics, were not rooted in radical economic and social reforms, which both sides advocated, but rather in their divergent positions on such issues as national sovereignty, borders, and Polish-Soviet relations.

[1] Instead, the Soviets commonly surrounded, disarmed and arrested the Underground's military authority members and its civilian representatives, instituting their own administrative structures instead.

[43] A number of prominent leaders of the Underground State, including the Government Delegate, Jan Stanisław Jankowski and the last AK Commander-in-Chief, General Leopold Okulicki, who decided to reveal themselves and upon the Soviet invitation begun open negotiations with the communist authorities, were arrested and sentenced by the Soviets in Moscow in the infamous Trial of the Sixteen (arrests were carried out in March 1945, and the trial itself took place in June that year).

[1][43][53][54][55] On 27 June 1945 the Council of National Unity held its last session, issuing a 12-point declaration demanding that the Soviet army leave Poland and the repression of the non-communist political parties cease.

[19][61] Following the rigged Polish legislative election of 1947, the few independent politicians like Mikołajczyk who attempted to form an opposition were threatened with arrests, retired or emigrated.

[66] Only the PPR, however, opposed to Polish independence and supporting full inclusion of Poland in the Soviet Union, was seen as completely outside the framework of the State; the other groups were seen as a justifiable opposition.

[76][77] The Armia Krajowa's primary resistance operations were the sabotage of German activities, including transports headed for the Eastern Front in the Soviet Union.

[63] They tied down significant German forces, worth at least several divisions (upper estimates suggest about 930,000 troops), diverting much-needed supplies, while trying to support the Soviet military.

[86] For decades, research on the Polish Underground State was restricted, largely because the communist People's Republic of Poland did not wish to fully acknowledge the role of the non-communist resistance.

[73][88] The limited research devoted to the Underground State that did take place was done mainly by Polish émigré historians living in the West.

[94] Scholars who chose to investigate the Underground State were also confronted with the issue of its uniqueness (no country or nation has ever created a similar institution), and hence, the problem of defining it.

[95] Salmonowicz concluded that "This constitutional continuity, real performance of the state's functions on its past territory and the loyalty of a great majority of Polish society were the most significant elements of its existence.