Final answer:
In 1991, 90% of Kosovo's population was comprised of Albanian Muslims, who were seeking independence from Serbian control. This ethnic majority in Kosovo played a central role in the political and ethnic conflicts during the breakup of Yugoslavia.
Step-by-step explanation:
The ethnic group that made up 90% of the population in Kosovo in 1991 was the Albanian Muslims. Kosovo was a region that experienced significant ethnic and political tensions during the breakup of Yugoslavia.
President Miloševik of Serbia sought to maintain control over Kosovo, asserting its importance to Serbian history and the Orthodox Church.
In contrast, the Albanian Muslims desired independence from Serb rule. This aspiration for autonomy and resistance to Serb control grew among the majority Albanian population, leading to increased conflicts and the eventual intervention by NATO in 1999.
The information provided showcases the ethnic complexities and political turmoil that characterized the region during the early 1990s, eventually contributing to widespread violence and the displacement of people.
Kosovo's status remained unresolved for many years thereafter, highlighting the enduring challenges of nationalism, ethnicity, and political geography in the Balkans.