During the German invasion of Poland, which started World War II, Gostyń was captured by the Wehrmacht on September 6, 1939. During the Nazi German occupation of Poland Gostyń became the site of public executions, arrests and expulsions of Poles. First mass arrests and executions were carried out already in September 1939. On 21 October 1939 some 30 citizens of the town whose names were listed in the "Sonderfahndungsbuch Polen" (Special Prosecution Book-Poland) prepared by local German minority, were executed by an Einsatzkommando. Among the murdered were Gostyń's mayor Hipolit Niestrawski, Polish activists, officials, craftsmen and former Greater Poland insurgents. It was one of many massacres of Poles committed by Germany on 20-23 October 1939 across the region in attempt to pacify and terrorize the Polish population. Mass expulsions began on 4 December 1939, with up to 2,000 Poles deported to General Government on the orders of SS-Standartenführer Ernst Damzog stationing in Poznań. Between spring of 1940 and 15 March 1941 additional 3,222 were deported. , Polish officer and pre-war chairman of the local football club Kania Gostyń, was murdered by the Soviets in the Katyn massacre in 1940.