Diệm's removal and assassination set off a period of political instability and declining legitimacy of the Saigon government. General Dương Văn Minh became president, but he was ousted in January 1964 by General Nguyễn Khánh. Phan Khắc Sửu was named head of state, but power remained with a junta of generals led by Khánh, which soon fell to infighting. Meanwhile, the Gulf of Tonkin incident of 2 August 1964 led to a dramatic increase in direct American participation in the war, with nearly 200,000 troops deployed by the end of the year. Khánh sought to capitalize on the crisis with the Vũng Tàu Charter, a new constitution that would have curtailed civil liberties and concentrated his power, but was forced to back down in the face of widespread protests and strikes. Coup attempts followed in September and February 1965, the latter resulting in Air Marshal Nguyễn Cao Kỳ becoming prime minister and General Nguyễn Văn Thiệu becoming nominal head of state.