Adoption of the new Constitution and introduction of the traditional chequered flag

The Croatian Parliament (Sabor) unanimously adopted a new Constitution under which the Republic of Croatia, still a member of the Yugoslav Federation, was established as a democratic and welfare state. The red Communist star, appearing since 1945 on the tricolour red, white and blue Croatian flag, was replaced by the historical red and white checkerboard coat of arms, in use in the Kingdom of Croatia since the Middle Ages.

First fatal ambushes by Serb separatists

Seven months after the beginning of the separatist insurgency supported by the Yugoslav Army, a Croatian policeman was killed by Serb militiamen in an ambush near Plitvice Lakes. After declaring their separation from Croatia on 28 February, the Serb separatist leaders proclaimed on 1 April they would be uniting with Serbia, an act they tried to legitimize subsequently by way of an illegal referendum held on 12 May 1991. On 2 May, the escalation of violence was raised to new heights after separatists ambushed 12 Croatian policemen, killing them and mutilating their bodies.

Text on the poster: "Serbian people in one state / Vote for annexation".