 Unknown to the Việt Minh, President Harry S. Truman, Prime Minister Winston Churchill and Premier Joseph Stalin had already decided the future of postwar Vietnam at a summit meeting at Potsdam.They agreed that the country would be occupied temporarily to get the Japanese out; the northern half would be under the control of the Nationalist Chinese and the southern half under the British.On 9 September, the Nationalist Chinese forces crossed the border and quickly took control of the north, while on 12 September, the British Indian Army arrived in Saigon.