Viet Minh attack South Vietnamese provincial capitals belying American belief that the war is drawing to a close. US launches brutal counterattack. US troops execute over 200 men, women and children in the village of My Lai. The massacre is captured by an army photographer. US troops in Vietnam peak at 536,000.
Marines secretly invade Laos.
US troops decline to 475,000. Congress later bans US combat forces in Cambodia and Laos. South Vietnamese troops invade Laos. US mines Haiphong Harbor and intensifies bombing of North Vietnam. Congress bans bombing of Cambodia, bans military expeditures anywhere in Indochina, and passes War Powers Act, requiring the President to consult Congress before committing troops.