If it was in fact an assassination, then that is probably why
Kennedy issued an nsa or sam or some memorandum numbered 263 [look that up as it may be the incorrect number] ordering down the troops in Nam [between 10 and 20 thousand stationed in the south] by 1000, after he was killed Johnson, as the story goes, drew up memorandum 264 or 265 [look that up as well] during the Kennedy funeral procession reversing Kennedy's orders and flooding Nam with hundreds of thousands of troops by 65...the war was on