The delegation was headed by Deputy Mayor Milan Bandic, who afterwards gave a reception for wartime military commanders and representatives of associations of Homeland War veterans.
Operation Flash was launched on the morning of May 1, 1995 and was completed next day. During the 31 hours, Croatian forces managed to retake 500 square kilometres of land from rebel Serb forces and regain control of the Zagreb-Lipovac highway.
About 7,200 Croatian soldiers and police officers were involved in the lightning offensive, 42 of whom were killed and 162 wounded.
The operation enabled the start of reconstruction of the Western Slavonia region and return of people displaced by war.
In retaliation for the defeat, Serb insurgents fired missiles with cluster munitions on Zagreb on May 2 and 3, 1995, killing six people and wounding 175, of whom 39 seriously.
The Hague-based International Criminal Tribunal for the former Yugoslavia (ICTY) later indicted Serb rebel leader Milan Martic for ordering the attacks.