Taking the example of Serbs in northern Dalmatia, Lika, Banovina and Kordun, Orthodox Serbs in Western Slavonia, took part in the rebellion against the Croatian government^{[citation needed]} that would result in creation of the RSK. The area under rebel control was known as the Serbian Autonomous Oblast of Western Slavonia (Srpska Autonomna oblast Zapadna Slavonija)^{[citation needed]}. It was proclaimed in August 1991, during the escalation of the conflict, and formally joined the rest of rebel areas later in the year.

Initially, the territory of the SAO Western Slavonia was relatively large and the rebel forces could theoretically advance north to the Hungarian border and sever the link between Zagreb and Osijek. In such case the Virovitica-Sisak-Karlovac-Karlobag line would have been established.

In reality, the territory of the SAO Western Slavonia was mostly hills and forests with relatively poor communication infrastructures. Establishing and maintaining a base for such ambitious operations required more resources than the Serbian government was willing or able to invest. As a result, the SAO Western Slavonia didn't receive as much support from the Yugoslav People's Army as other parts of the RSK did. Most of its forces were local militias, poorly trained, lightly armed and unable to match their Croatian counterparts.^{[citation needed]}

This situation became apparent in late 1991 when local Croatian forces, armed and equipped from the captured JNA garrison in nearby Varaždin, conducted a series of offensives which ultimately reduced SAO Western Slavonia to a relatively small pocket centered around Okučani. It is believed that the Sarajevo armistice in January 1992 saved the forces of the Serb Krajina from being pushed across the River Sava and the SAO Western Slavonia from disappearing altogether.

The position of the rebel area in Western Slavonia became even more precarious with the escalation of Bosnian War. It became quite clear that the position of the rebels in Western Slavonia in such circumstances was untenable in the long run. Veljko Džakula and a group of other local rebel Serb politicians in 1992 and 1993 started secret negotiations with the Croatian government about eventual peaceful transfer of the rebel areas in Western Slavonia under Croatian authority.

On February 18, 1993 Croatian and local Serb leaders (led by Džakula) signed the Daruvar Agreement. The Agreement was kept secret and was working towards normalizing life for the locals on the battlefield line.^[3] However, the Knin authorities learned of the deal - and Džakula was arrested by the authorities of the RSK and replaced by hardliners.

The UN negotiators saw this development as an encouraging sign that the conflicts in the former Yugoslavia could be ended peacefully. The authorities of Croatia and the rebel areas in Western Slavonia were encouraged to take part in various confidence building programs like family reunions. Some of those programs began to bear fruit in late 1994. The most important was the opening of the Zagreb-Županja Motorway for Croatian traffic.

In late April 1995 there was an inter-ethnic incident which resulted in the deaths of a number of Croats and Serbs and in the disruption of the motorway. Hrvoje Sarinic, Franjo Tudjman's former Cabinet Chief, confirmed under cross-examination at the Milosevic trial a transcript detailing the then Croatian leadership's plan to stage an incident as a pretext^[4] for the offensive on May 1st, although no linkage was shown to the abovementioned incident. Hrvoje Sarinic, as a witness at the same trial, downplayed the significance of such a plan, pointing out there were many incidents daily, and to his own exepriences at being refused entry on the motorway, problems with reopening the oil pipeline, and finally stating that he was "very astonished that any incident was needed, because it was quite legitimate to free part of the country that had been occupied"^[4].

Timeline

On the early morning of May 1st, Croatian Army forces (which included the elite 3rd and 5th Guards Brigades) and Special Police units began their advance from three directions. Over 7,200 soldiers and policemen participated in the operation.

Rebel forces were quickly overwhelmed and in a few hours time local commanders and civilian authorities issued orders for evacuation across the River Sava into Bosnia's Republika Srpska.

By the afternoon of May 2nd all rebel forces were evacuated and the Croatian Army had achieved all of its initial aims. One large group of rebel soldiers and civilians, including Džakula, failed to evacuate and had to surrender near Pakrac. The operation produced a total of around 1,500 Serb POWs, the largest capturing of an enemy force to date in the war.

The forces of the RSK also launched a retaliatory action against civilian targets by launching a number of cluster shells on Zagreb on May 2nd and 3rd. The attack killed 7 and injured at least 175 people. On that very same day the leader of the RSK, Milan Martić publicly took responsibility for the shelling, and that statement was used against him at his ICTY trial.

Map of the territorial division of the Srpske vojske Krajine (SVK), 1995.

The documentation-information center Veritas announced that "on May 1, 1995, Croatian armed forces conducted an aggression on the Western Slavonia area where some 15,000 Serbs lived under UN protection".^[6] "In only 36 hours, 283 people were either killed or went missing, 57 of them women and nine children. The Croats buried 168 Serbs, mostly listing them as "unidentified", and those bodies have to date not been exhumed and indentified," the center stated.^[7]

The president of the Association of Refugee Organizations of Serbs from Croatia, Milojko Budimir, told reporters in Belgrade today after the church service for the victims that even after 14 years, no one has been held accountable for the crimes committed against the Serbs, "neither in front of the Hague Tribunal, nor in front of the domestic courts".^[8]

Some 30,000 Serbs were forced to leave their homes. ^[9] While there have been returnees since the end of the war, to all parts of Croatia, the number of returnees is small in comparison to the pre-war population.