Barbara Tuchman on the U.S. military's first involvement in Vietnam

A week after the Japanese surrender in August 1945, a Viet-Minh congress in Hanoi proclaimed the Democratic Republic of Vietnam and after taking control in Saigon declared its independence, quoting the opening phrases of the American Declaration of Independence of 1776.  In a message to the UN transmitted by the OSS, Ho Chi Minh warned that if the UN failed to fulfill the promise of its charter and failed to grant independence to Indochina, "we will keep on fighting until we get it."

[...]

Self-declared independence lasted less than a month.  Ferried from Ceylon [Sri Lanka] by American C-47s, a British general and British troops with a scattering of French units entered Saigon on 12 September, supplemented by 1500 French troops who arrived on French warships two days later.  Meanwhile, the bulk of two French divisions had sailed from Marseilles and Madasgar on board two American troopships in the first significant act of American aid...  Afterward, the State Department, closing the stable door, advised the War Department that it was contrary to United States policy "to employ American flag vessels or aircraft to transport troops of any nationality to or from the Netherlands East Indies or French Indochina, or to permit the use of such craft to carry arms, ammunition or military equipment to those areas."

~ Barbara Tuchman, The March of Folly, pp. 240-241