What new war tactic, employed by the U.S. marines in 1965, particularly disgusted John Paul Vann and why?

John Paul Vann was repulsed by the tactic of burning villages. Seen as a way to flush out hidden pockets of Vietcong combatants in South Vietnam, John Paul Vann saw only the rapid escalation in collateral damage (i.e., innocent non-combatants), who were displaced, injured, and killed by the policy.