president johnson and vietnam By lennir Nov 22, 1963 jonson becomes president after kennedy is assassinated Period: Nov 22, 1963 to Mar 31, 1968 President Johnson Johnson announce he will not seek re-election Feb 10, 1964 allows covert operation against north vietnam . Feb 10, 1965 increase in American troop involvement . Feb 10, 1968 tet offfenive it shocvked them and it scared the people in the us