Sihanouk came to believe that communist triumph in Southeast Asia was inevitable and that Cambodia's military was incapable of defeating the North Vietnamese, even with U.S. support. If Cambodia (and his rule) was to survive, he would have to make a bargain with the devil. On 10 April 1965 he broke off diplomatic relations with the U.S. and swung politically to the left. This move was not without reason. To gain foreign support, both economic and political, Sihanouk turned to the People's Republic of China. One of the terms of the agreement between Sihanouk and Premier Zhou Enlai was that Cambodia would allow the use of its eastern border by the North Vietnamese in their effort to reunify the two Vietnams.