In addition to the issues of Quebec sovereignty, a number of crises shook Canadian society in the late 1980s and early 1990s. These included the explosion of Air India Flight 182 in 1985, the largest mass murder in Canadian history; the École Polytechnique massacre in 1989, a university shooting targeting female students; and the Oka Crisis of 1990, the first of a number of violent confrontations between the government and Indigenous groups. Canada also joined the Gulf War in 1990 as part of a United States–led coalition force and was active in several peacekeeping missions in the 1990s, including the UNPROFOR mission in the former Yugoslavia. Canada sent troops to Afghanistan in 2001 but declined to join the United States–led invasion of Iraq in 2003.