One of the biggest anti-partisan operations by the communist authorities took place from 10 to 25 June 1945, in and around the Suwałki and Augustów regions of Poland. The "Augustów roundup" () was a joint operation of the Red Army, the Soviet NKVD, and SMERSH battalions, with assistance from Polish UB and LWP units, against Armia Krajowa resistance fighters. The operation extended into the territory of occupied Lithuania. More than 2,000 suspected anti-communist Polish fighters were captured and detained in Soviet internment camps. About 600 of the "Augustow Missing" are presumed to have died in Soviet custody, their bodies buried in unknown mass graves on the present territory of Russia. The Polish Institute of National Remembrance has declared the 1945 Augustów roundup to be "the largest crime committed by the Soviets on Polish lands after World War II."