In June 1991, the republics of Slovenia and Croatia declared independence from Yugoslavia, beginning the country's break up. The next month, the Yugoslav army—largely composed of Serbs and controlled by Slobodan Milosevic—invaded Croatia, justifying the act as a means to protect the Serbian minority there.

The invasion of Croatia by the Serb-controlled Yugoslav People's Army (JNA) and local Serb paramilitaries in 1991 was primarily driven by the breakup of Yugoslavia and the clash between Croatian independence and Serbian nationalism. When Croatia declared independence in June 1991, the Serbian leadership under Slobodan Milošević sought to protect ethnic Serb minorities living within Croatia and to prevent the secession. More broadly, the goal was the creation of a "Greater Serbia"—an attempt to annex territories in Croatia (like Krajina and Slavonia) where Serbs were a majority or significant minority, effectively redrawing borders by force. The JNA, which was supposed to be a neutral federal force, sided with the Serbian cause, leading to the occupation of nearly one-third of Croatian territory. This resulted in a brutal four-year War of Independence characterized by sieges (like Vukovar), ethnic cleansing, and intense urban warfare, which only ended in 1995 with Croatia's successful counter-offensives and the international recognition of its sovereign borders.