On October 2–5, 1939, Kock was the site of the last battle between Poland and Germany during the joint German-Soviet invasion of Poland, which started World War II. Afterwards it fell under German occupation, and already in October 1939, the Germans carried out executions of Poles at the local cemetery. During the occupation, the Jewish half of the Kock population, about 2,200 of the town's 4,600 population, was murdered or died of disease and starvation in the ghetto set up by the Germans in Kock. Kock was one of centers of the Home Army, whose units (27th Volhynian Home Army Infantry Division) freed the town on July 22, 1944. Afterwards, the advancing Soviets disbanded Polish soldiers, however Kock was re-captured by Polish anti-Communist resistance (May 1, 1945).