By March 1991, tensions between Croats and Serbs escalated into the Croatian War of Independence. Following a referendum on independence that was largely boycotted by Croatian Serbs, the Croatian parliament officially adopted independence on 25 June. The Republic of Serb Krajina (RSK) declared its intention to secede from Croatia and join the Republic of Serbia while the Government of the Republic of Croatia declared it a rebellion. Between August 1991 and February 1992, the RSK initiated an ethnic cleansing campaign to drive out the Croat and non-Serb population from RSK-held territory, eventually expelling as many as 250,000 people according to Human Rights Watch. Croatian forces also engaged in ethnic cleansing against Serbs in Eastern and Western Slavonia and parts of the Krajina on a more limited scale. On 4 August 1995, the Croatian Army (HV) launched Operation Storm to retake the Krajina region which was completed successfully by 7 August. The Operation resulted in the exodus of approximately 200,000 Serbs from Krajina while those Serbs who were unable or unwilling to leave their homes, primarily the elderly, were subjected to various crimes. The ICTY puts the number of Serb civilians killed at 324.