The Haditha massacre was a series of killings on November 19, 2005, in which a group of United States Marines killed 24 unarmed Iraqi civilians. The killings occurred in the city of Haditha in Iraq's western province of Al Anbar. Among the dead were men, women, elderly people and children as young as 1, who were shot multiple times at close range while unarmed. The ensuing massacre took place after an improvised explosive device exploded near a convoy, killing a lance corporal and severely injuring two other marines. The immediate reaction was to seize 5 men in a nearby taxi and execute them on the street.

3rd Battalion, 1st Marines (3/1) is an infantry battalion in the United States Marine Corps based out of Camp Horno on Marine Corps Base Camp Pendleton, California. Nicknamed the "Thundering Third", the battalion consists of approximately 1,200 Marines and Sailors and falls under the command of the 1st Marine Regiment and the 1st Marine Division.