On the eve of the Tet holiday, North Vietnamese and Viet Cong forces launch surprise attacks on cities and military bases throughout the south, suffering devastating losses but casting grave doubt on Johnson’s promise that there is “light at the end of the tunnel.” The president decides not to run again and the country is staggered by assassinations and unrest.
http://www.pbs.org/video/things-fall-apart-january-1968-july-1968-r5aqgg/