LBJ, Jan. 10, 1967: We have chosen to fight a limited war in Vietnam in an attempt to prevent a larger war--a war almost certain to follow, I believe, if the Communists succeed in overrunning and taking over South Vietnam by aggression and by force. I believe, and I am supported by some authority, that if they are not checked now the world can expect to pay a greater price to check them later.
GWB, Jan. 10, 2007: The challenge playing out across the broader Middle East is more than a military conflict. It is the decisive ideological struggle of our time…In the long run, the most realistic way to protect the American people is to provide a hopeful alternative to the hateful ideology of the enemy – by advancing liberty across a troubled region.
Not much to add here -- the words of Lyndon Johnson and George W. Bush pretty much speak for themselves.
Two things, though. First of all, only 7,917 American troop had died in Vietnam through the end of 1966, or ten days before Johnson's speech. From the beginning of 1967 though the end of the war, an addition 50,285 -- more than six times as many -- Americans would lose their lives.