Since the Gulf War in 1991, Iraq had been restricted by the United Nations (UN) from developing or possessing such weapons. It was also required to permit inspections to confirm Iraqi compliance. Bush repeatedly backed demands for unfettered inspection and disarmament with threats of invasion. On 20 March 2003, a multinational alliance containing the armed forces of the United States and United Kingdom launched an invasion of Iraq in 2003. After the withdrawal of U.S. troops from Iraq in 2011, a number of failed Iraqi peace initiatives were revealed.