Shortly after the proclamation of the SAO Western Slavonia, rebel Serb forces, assisted by the Serb-led
Yugoslav People's Army (JNA) and Serb paramilitary forces (from Serbia and Bosnia-Herzegovina), took
Okučani and
Daruvar, threatening to sever
Slavonia from Croatia proper. At this time, the area under Serbian control was relatively large, although the majority of the region was hilly and forested with poor infrastructure. During the next months, there was fierce battle for
Pakrac as paramilitaries ethnically cleansed Croats from newly captured Western Slavonic districts. Most of the region was patrolled by poorly equipped Serbian militias drawn from the local Serb villages, and with JNA resources widely distributed at a precarious time, they were not in position to effectively dissect Croatia. On October 31, 1991, Croatian forces launched
Operation Otkos 10 securing the
Bilogora hills. Following this success, the Croat
Operation Orkan 91, on December 12, pushed back the Serb/Yugoslav forces into a small pocket only a fraction of the initial territory controlled. In the operation,
Daruvar was liberated. During their retreat, Serbian paramilitaries committed the
Voćin massacre. On January 2, 1992, the UN brokered a ceasefire in Sarajevo, it is possible that this stopped the Croatian forces from eliminating the rebel Serb presence in Western Slavonia. On February 18, 1993, Croatian and local Serb leaders signed the
Daruvar Agreement. The Agreement was kept secret and was working towards normalising life for the locals on the battlefield line. However, the rebel Serb authorities from Knin learned of the deal and arrested the rebel Serb leaders responsible for it. The Serb enclave of Western Slavonia was eliminated and the area reintegrated into Croatia in two days in May 1995, during
Operation Flash. In retaliation for this thorough defeat,
Milan Martić launched
rockets at Zagreb. ==Administrative divisions==