Following the invasion of Poland and the outbreak of the Second World War in September 1939, Kępno was occupied by the Wehrmacht and on September 6–7, 1939 the "Einsatzgruppe III" entered the town to commit atrocities against Poles. Some Poles from Kępno were murdered by German troops already on September 7, 1939 in the nearby village of Wylazłów. The town was annexed by Nazi Germany, renamed "Kempen" and administered as part of the county or district ("kreis") of the same name within Reichsgau Wartheland. Its population was subject to segregation, Germanisation, confiscation of property, arrests, expulsions, deportations to forced labour, imprisonment in Nazi concentration camps and executions. The Germans established and operated a Nazi prison in the town. Polish monuments were destroyed. The Polish resistance movement was organized in Kępno in November 1939. Red Army troops took the town on January 21, 1945 and with the end of the war, the town returned to Poland, although with a Soviet-installed communist regime, which remained in power until the Fall of Communism in the 1980s. The Polish resistance movement remained active in the town, and in September 1945 it captured the local communist police station and liberated the prisoners.