In 1955, the Prime Minister of South Vietnam Ngô Đình Diệm faced a severe challenge to his rule over South Vietnam from the Bình Xuyên criminal gang and the Cao Đài and Hòa Hảo religious sects. In the Battle of Saigon in April, Diệm's army eliminated the Bình Xuyên as a rival and soon also reduced the power of the sects. The United States, which had been wavering in its support of Diệm before the battle, strongly supported him afterwards.Diệm declined to enter into talks with North Vietnam concerning an election in 1956 to unify the country. Diệm called a national election in October and easily defeated Head of State Bảo Đại, thus becoming President of South Vietnam.