In the final months of World War II, as Yugoslav Partisan forces and the Red Army drove Axis troops out of Serbia, members of the Partisan movement and the incoming communist authorities carried out mass killings of people categorized as war criminals, collaborators (quislings) and ideological opponents. Most of these killings occurred between October 1944 and May 1945. According to a state investigation, at least 55,973 people died during this period from causes including summary execution and illness in retention camps; the vast majority of deaths were deliberate executions carried out without trial. Victims came from multiple ethnic backgrounds, predominantly Germans, Serbs, Albanians and Hungarians. Some analysts have argued the killings were not centrally planned but were unorganized reprisals carried out amid post-war disorder, or that some recorded as executed instead died in combat against Partisan forces. Estimates of the total number of victims vary widely, from roughly 80,000 to more than 100,000 for Serbia as a whole, reflecting ongoing controversy and incomplete investigation.
In central Serbia, an estimated 30,000 people were killed. According to Milovan Đilas, communist leaders decided before entering Belgrade that followers of the wartime pro-Axis Government of National Salvation should be liquidated immediately, viewing Belgrade as a center of "reaction" requiring thorough purging of anti-communist elements. This included figures from cultural, political and public life under German occupation, as well as members of the rival Chetnik movement defeated in the parallel civil war.
In Vojvodina, encompassing Bačka, Banat, Baranja and Syrmia, most executions took place under a military administration established in October 1944 under Brigadier General Ivan Rukavina. Ethnic German victims in Vojvodina are estimated between 17,000 and over 59,000, with a prison camp system operating from 1944–1946 in which ethnic Germans faced forced labor, torture, and death from starvation and disease; some were transferred to Soviet forces for labor in Siberia. Serb victims in Vojvodina are estimated at 23,000–24,000, including mass arrests and executions of prominent Novi Sad residents—among them the city's former mayor, doctors, industrialists and intellectuals—following the Partisan entry into Novi Sad in October 1944. Estimates of executed Hungarians in Vojvodina vary enormously, from roughly 1,000 to as many as 40,000–50,000 depending on the source, with the state commission's 2014 registry listing 6,112 Hungarian victims. Members of the Rusyn community in Đurđevo were also targeted, with several hundred reportedly executed; the state commission recorded 40 Rusyn victims.
Multiple investigative bodies have examined these events since the war, including a 1943 federal war-crimes commission, a 2001 Vojvodina provincial surveying committee, a 2004 Vojvodina Academy study, a 2009 Serbian State Commission for secret burial places (which produced the 55,973-name registry), and a joint Hungarian-Serbian academic commission formed in 2010. In June 2013, the Serbian Parliament adopted a declaration condemning the massacres and application of collective guilt against Hungarians in Vojvodina; Hungarian President János Áder subsequently apologized in Belgrade for wartime crimes committed against Serb and Jewish civilians during the Hungarian occupation.