Motley, while this is a good link it doesn't give enough of the context; IMO Karen Faust's letter also has merit.  Looking back on memories from an incredible  era of long ago, I seem to recall that during WWII the French, under Vichy, were nominal allies of the Japanese who occupied French Indo China.   They were opposed by the Viet Minh under Ho Chi Minh  who were a mix of nationalists and Communists; we supported them against the Japanese when possible.
After the war the French marched in and, in total contradiction of Allied  principles forcefully  tried to regain control of their old colony, and were opposed by the Viet Minh's independence movement.  While we were sympathetic to their principles, Truman  feared Communism, which had  gained control of much of Europe and Asia,  more-- and thus foolishly decided to do what we could to help the French-- and as they collapsed we decided we had to move in to fill the vacuum..... and the rest, as I recall it, is history.