During World War II, the Kingdom of Yugoslavia was invaded and partitioned by the Axis powers, and Kragujevac were occupied by Nazi Germany soldiers and underwent a number of tragic days during war. The local population were suppressed and many Serbian civilians, as well Roma and Jews, were murdered or have perished in concentration camps. The follow, many citizens of Kragujevac joined the resistance in the country and fought against the fascist occupation. The Nazis had issued an order to kill 50 Serbian civilians for every wounded German soldier and 100 for each German soldier killed. Especially tragic was the days between 19–21 October 1941, when German Nazis assembled thousand of males from the town between the ages of sixteen and sixty, and were executed, today known as the Kragujevac massacre. Among the killed was many boys taken directly from schools and their teachers, which had a strong influence on subsequent generations of the city. The massacre was a direct reprisal for the German losses in battles. The executions in Kragujevac occurred although there had been no attacks on members of the Wehrmacht in this city, for the reason that not enough hostages could be found elsewhere. Radnički lost during the war numerous players, club officials and a whole generation of club supporters. Therefore, comes mainly the especially deep-rooted antifascist attitude of the city, the club and its supporters. To commemorate the victims of the massacre, the whole village of Šumarice, where the killings took place, was turned into a memorial park, called Šumarice Memorial Park, and it was built the "Museum of Genocide" in Kragujevac, not so far from the stadium. After the liberation of Kragujevac in 1944, the club continues to rapidly develop into a bigger football club in the country.