Operation Flash () was a brief Croatian Army (HV) offensive conducted against the forces of the self-declared proto-state Republic of Serbian Krajina (RSK) from 1–3 May 1995. The offensive occurred in the later stages of the Croatian War of Independence and was the first major confrontation after ceasefire and economic cooperation agreements were signed between Croatia and the RSK in 1994. The last organised RSK resistance formally ceased on 3 May, with the majority of troops surrendering the next day near Pakrac, although mop-up operations continued for another two weeks.
Operation Flash was a strategic victory for Croatia resulting in the capture of a salient held by RSK forces centred in and around the town of Okučani. The town, which sat astride the Zagreb–Belgrade motorway and railroad, had presented Croatia with significant transport problems between the nation's capital Zagreb and the eastern region of Slavonia as well as between non-contiguous territories held by the RSK. The area was a part of United Nations Confidence Restoration Operation (UNCRO) Sector West under the United Nations Security Council peacekeeping mandate in Croatia. The attacking force consisted of 7,200 HV troops, supported by the Croatian special police, arrayed against approximately 3,500 RSK soldiers. In response to the operation, the RSK military bombarded Zagreb and other civilian centres, causing seven fatalities and injuries to 205.
Forty-two HV soldiers and Croatian policemen were killed in the attack and 162 wounded. RSK casualties are disputed—Croatian authorities cited the deaths of 188 Serb soldiers and civilians with an estimated 1,000–1,200 wounded. Serbian sources, on the other hand, claimed that 283 Serb civilians were killed, contrary to the 83 reported by the Croatian Helsinki Committee. It is estimated that out of 14,000 Serbs living in the region, two-thirds fled immediately with more following in subsequent weeks. By the end of June, it is estimated that only 1,500 Serbs remained. Subsequently, the personal representative of the Secretary-General of the United Nations Yasushi Akashi criticised Croatia for "mass violations" of human rights, but his statements were refuted by the Human Rights Watch and to some extent by the United Nations Commission on Human Rights rapporteur Tadeusz Mazowiecki.
Background
The 1990 revolt of the Croatian Serbs was centred on the predominantly Serb-populated areas of the Dalmatian hinterland around Knin, parts of the Lika, Kordun, Banovina regions and in eastern Croatian settlements with significant Serb populations, as well as parts of western Slavonia centred on Pakrac and Okučani. In the early stages of the Log Revolution, tens of thousands of Serbs fled from Croatian controlled cities, leading to the formation of a single political entity known as the Republic of Serbian Krajina (RSK). The RSK's proclaimed intention to integrate politically with Serbia was viewed by the Croatian Government as an act of rebellion. By March 1991, the conflict had escalated to war—the Croatian War of Independence. In June 1991, with the breakup of Yugoslavia, Croatia declared its independence, which came into effect on 8 October after a three-month moratorium. From late October to late December 1991, the HV conducted Operations Otkos 10 and Orkan 91 recapturing 60% of RSK-occupied western Slavonia, resulting in Serbs fleeing from the area, while some were killed in a death camp in Pakračka Poljana. A campaign of ethnic cleansing was then initiated by the RSK against Croatian civilians and most non-Serbs were expelled by early 1993. After the end of the war, thousands of civilians murdered by the Serb troops were exhumed from mass graves.
As the Yugoslav People's Army (JNA) increasingly supported the RSK and the Croatian Police was unable to cope with the situation, the Croatian National Guard (ZNG) was formed in May 1991. The ZNG was renamed the Croatian Army (HV) in November. The establishment of the military of Croatia was hampered by a United Nations (UN) arms embargo introduced in September. The final months of 1991 saw the fiercest fighting of the war, culminating in the Battle of the barracks, the Siege of Dubrovnik, and the Battle of Vukovar. The western Slavonia area became the scene of a JNA offensive in September and October aimed at severing all transport links between the Croatian capital, Zagreb, and Slavonia. Even though the HV managed to reclaim much territory gained by the JNA advance in operations Otkos 10 and Orkan 91, it failed to secure the Zagreb–Belgrade motorway and railroad significant for the defence of Slavonia.