He points to a speech Kennedy gave in the summer of 1963, just months before his assassination, that suggested a very different trajectory for U.S. involvement in Vietnam. The evidence indicates Kennedy was unlikely to pursue the escalation that followed. Once Lyndon Johnson assumed the presidency, one of his first moves was to deploy troops and ramp up military engagement. The shift wasn't gradual. It was immediate and deliberate. The question becomes: what changes when leadership changes that abruptly? The policy reversal happened within months, not years. That timeline matters when you're trying to understand how decisions get made at the highest levels of power.