It was the first act of mass murder committed by the Ustaše upon coming to power, and presaged a wider Ustaše-perpetrated campaign of genocide against Serbs in the NDH that lasted until the end of the war.

The Ustaše forced Gudovac's surviving inhabitants to dig a mass grave for the victims and pour quicklime on the bodies to speed up decomposition.

Mladen Lorković, a senior Ustaše official, used his influence to have the detained men released and promised German ambassador Siegfried Kasche that the Croatian authorities would carry out a thorough investigation.

In 1928, Croatian Peasant Party (Hrvatska seljačka stranka, HSS) leader Stjepan Radić was shot and mortally wounded on the floor of the country's parliament by a Serb deputy.

[3] Following the 1938 Anschluss (union) between Germany and Austria, Yugoslavia came to share a border with the Third Reich and fell under increasing pressure as her neighbours became aligned with the Axis powers.

[9] Intending to secure his southern flank for the impending attack on the Soviet Union, Adolf Hitler began placing heavy pressure on Yugoslavia to join the Axis.

Two days later, a group of pro-Western, Serbian nationalist air force officers deposed Prince Paul in a bloodless coup d'état.

[12] The regiment had been mobilized in Bjelovar, and on 7 April was marching towards Virovitica to take up positions, when its Croat members revolted and arrested the Serb officers and soldiers.

[13] Led by Captain Ivan Mrak, the regiment disarmed a Yugoslav gendarmerie post in Garešnica and began marching back to Bjelovar alongside a band of Ustaše rebels under Mijo Hans.

[14] At around the same time, Julije Makanec, the Croat mayor of Bjelovar, joined Ustaše official Ivan Šestak and HSS representative Franjo Hegeduš in demanding that the VKJ surrender the town to the rebels.

Ustaše propaganda celebrated it as "an uprising of the Croatian people against the April War", claiming it showed that Croats wholeheartedly supported Yugoslavia's destruction.

[18] On 10 April, senior Ustaše commander Slavko Kvaternik proclaimed the establishment of the Independent State of Croatia (Nezavisna Država Hrvatska, NDH).

Pavelić reached Zagreb on 15 April, having granted territorial cessions to Italy at Croatia's expense and promised the Germans he had no intention of pursuing a foreign policy independent of Berlin.

[26] Ivan Garščić, a public notary, was appointed acting commander of the Bjelovar armoury and set about reorganizing local Ustaše formations.

Serb officers that had refused to surrender raided Croat homes, hoping to find food, money and civilian clothing that would make it easier for them to pass through German and Ustaše checkpoints.

[18] On 10 April, the Germans reached Bjelovar and set up a series of command posts but left the Ustaše in de facto control of the city.

Mišo Sabolek, a local Ustaše commander, reported: "Bjelovar and its surroundings are besieged by Serbs, who are ... killing and looting homes in the villages of Nart, Gudovac and the Česma forest."

"The disarming of Serbs ... is vital to securing the future of the young Croatian state," wrote Edmund Glaise-Horstenau, the German Plenipotentiary General in the NDH.

[27] Alarmed by the prospect of an armed rebellion in Bjelovar and the surrounding countryside, Kvaternik selected a broad area in and around the town where Serbs were to be "cleansed".

Kvaternik feared that these deaths would only increase the likelihood of an armed revolt and became even more wary when he heard rumours that Bjelovar's Serbs were planning an uprising to coincide with the feast day of St. George (Đurđevdan), on 6 May.

[31] Upon hearing news of the attack at the county jail, Kvaternik ordered the arrest of 200 Serb peasants from Gudovac and the neighbouring villages of Veliko and Malo Korenovo, Prgomelje, Bolč, Klokočevac, Tuk, Stančići and Breza.

[34] The action was personally supervised by Kvaternik and carried out by members of the local Croatian Peasant Guard, which had been turned into a "quasi-military unit" under the command of Martin Čikoš, whom the journalist Slavko Goldstein describes as a "sworn pre-war Ustaša".

Four stepped forward and offered their identification papers; three were permitted to return to their homes upon having their identities verified but the fourth was sent back among the Serbs because he was a communist.

"[34] The prisoners reached the field just after sunset and were ordered to line up in ranks and make a left face; the guards then raised their rifles and opened fire.

[39][40] Kvaternik and the Ustaše never attempted to conceal the killings, which were deliberately carried out in a relatively public space so as to cause terror among the Serb population.

[45] The historian Željko Karaula claims that the VKJ marched into several hamlets on 11 April and summarily executed eleven Croats that had refused to report for mobilization several days earlier.

[26] Goldstein posits that 25 of the 27 Croats whose deaths the Ustaše attributed to "Serb agitators" prior to the massacre had perished in combat operations during the rebellion of the 108th Regiment.

[47] Lorković maintained that the massacre in Gudovac was an "internal political issue under the jurisdiction of the Croatian government" and requested that the suspected perpetrators be handed over to the Ustaše.

[44] The National Archive in Bjelovar contains extensive documentation of the massacre, including a list of victims compiled by Ustaše officials in May 1941, in which many prisoners are described as being "shot as Chetniks".

[52] Pavelić also fled to Argentina, survived an assassination attempt by Yugoslav government agents in Buenos Aires in 1957, and died of his wounds in Madrid two years later.