Free-fire zones were places pounded with artillery or annihilated with napalm and bombs in an effort to drive out the enemy. American soldiers were authorized to shoot at anything that moved. Large swaths of the Mekong Delta, believed to be dominated by the Viet Cong, were declared free-fire zones. Some places were described as “Wild Wes-like shooting galleries.”

Villagers in free-fire zones were encouraged to move to “strategic hamlets,” but often they didn’t want to because their families had lived in their home villages for generations and they were afraid of losing them. If the staid they could be regarded as “target of opportunity” and fired upon.

The policy of village destruction, heavy bombardment, free-fire zones, “relocation” of peasants and other indignities created hundreds of thousands of displaced people and wounded. In Quang Ngai, the province that surrounded My Lai, 70 percent of the villages had been destroyed by B-52 bombs, bulldozers, napalm, artillery fire, lighters and matches, gun fire and other means. Some 40 percent of the population lived in refugee camps and civilian casualties were in the neighborhood of 50,000 a year.

“The wreckage was all around us,” Tim O’Brien in the New York Times wrote, so common it seemed part of the geography, as natural as any mountain or river. Wreckage was the rule. Brutality was S.O.P. Scaled children, pistol-whipped women, burning hootches, free-fire zones, body counts, indiscriminate bombing and harassment fire, villages in ash, M-60 machine guns hosing down dark tree lines and any human life behind them.”