In August 1990, Iraqi forces invaded and annexed Kuwait. After a series of failed diplomatic negotiations, the United States led a coalition to remove the Iraqi forces from Kuwait, in what became known as the Gulf War. On 26 February 1991, the coalition succeeded in driving out the Iraqi forces. As they retreated, Iraqi forces carried out a scorched earth policy by setting oil wells on fire. During the Iraqi occupation, more than 1,000 Kuwaiti civilians were killed. In addition, more than 600 Kuwaitis went missing during Iraq's occupation; remains of approximately 375 were found in mass graves in Iraq.