The Augustów roundup (Polish Obława augustowska) was a military operation against the Polish World War II anti-communist partisans and sympathizers following the Soviet takeover of Poland. The operation was undertaken by Soviet forces with the assistance of Polish communist units, and conducted from July 10 to July 25, 1945, in Suwałki and Augustów region (Podlasie) of northern Polish People's Republic. Out of 2,000 arrested by the Soviet forces, about 600 have disappeared. They are presumed to have been executed and buried in an unknown location in present-day Russia or Belarus. Polish Institute of National Remembrance has declared the 1945 Augustów roundup "the largest crime committed by the Soviets on Polish lands after World War II". The crime has been called "second Katyn", "small Katyn", "little Katyn" or "Podlaski Katyn" in today's Poland, in reference to the Katyn massacre that occurred in 1940. Background In the aftermath of the joint German-Soviet invasion of Poland, the Polish government evacuated to the West and created the Polish Underground State. While no war was declared between Poland and the Soviet Union, the relations were tense, and eventually broke down in 1943 in the aftermath of the revelations of the Katyn massacre. The Soviets eventually created their own Polish communist puppet government, the Polish Committee of National Liberation (Polski Komitet Wyzwolenia Narodowego, PKWN) and refused to deal with the Underground State just like they refused to deal with the government-in-exile; its leaders and soldiers on "liberated" Polish territories were persecuted. While the Underground State's military arm, Armia Krajowa, officially disbanded on January 19, 1945, to avoid armed conflict with the Soviets and a civil war, some refused to lay down their arms; others found it simply difficult to return to civilian life, as those with ties to non-communist resistance were discriminated against by the authorities. Operation The operation was undertaken by Soviet forces of the Red Army, the NKVD and SMERSH with the assistance of Polish UB and LWP units, and conducted from July 12 to July 28, 1945, in the Suwałki and Augustów regions of northern Polish People's Republic. This operation included not only Polish communist territories, but also former Polish territories annexed by the Soviet Union and given to the Lithuanian SSR (see Soviet occupation of Lithuania). Aftermath More than 2,000 Polish (some estimate as many as 7,000) alleged anti-communist fighters and sympathizers were arrested and interrogated in two waves of mass arrests.