Between October 18-October 21, 1941, German soldiers go on a rampage, killing thousands of Yugoslavian civilians, including whole classes of schoolboys, in what has become known as the Kragujevac massacre.

Despite attempts to maintain neutrality at the outbreak of World War II, Yugoslavia finally succumbed to signing a “friendship treaty” with Germany in late 1940, finally joining the Tripartite “Axis” Pact in March 1941. The masses of Yugoslavians protested this alliance, and shortly thereafter the regents who had been trying to hold a fragile confederacy of ethnic groups and regions together since the creation of Yugoslavia at the close of World War I fell to a coup, and the Serb army placed Prince Peter into power. The prince—now the king—rejected the alliance with Germany-and the Germans retaliated with the Luftwaffe bombing of Belgrade, killing about 17,000 people.

With Yugoslavian resistance collapsing, King Peter removed to London, setting up a government-in-exile. Hitler then began to carve up Yugoslavia into puppet states, primarily divided along ethnic lines, hoping to win the loyalty of some-such as the Croats-with the promise of a postwar independent state. (In fact, many Croats did fight alongside the Germans in its battle against the Soviet Union.) Hungary, Bulgaria and Italy all took bites out of Yugoslavia, as Serb resisters were regularly massacred. In October of 1941, 2,300 men and boys were murdered in Kragujevac, Kraljevo saw 7,000 more killed by German troops, and in the region of Macva, 6,000 men, women, and children were murdered.

Serb partisans, fighting under the leadership of the socialist Josef “Tito” Brozovich, won support from Britain and aid from the USSR in their battle against the occupiers. “The people just do not recognize authority…they follow the Communist bandits blindly,” complained one German official reporting back to Berlin.