Which US Army division was responsible for the My Lai Massacre area in 1968?

The Americal Division was the U.S. Army division responsible for the My Lai area in 1968.

The Americal, formally the 23rd Infantry Division, operated in South Vietnam’s I Corps, including Quảng Ngãi Province. Its subordinate 11th Infantry Brigade formed Task Force Barker, the force assigned to search for Viet Cong units around Sơn Mỹ village on March 16, 1968. Soldiers from Charlie Company, 1st Battalion, 20th Infantry, and other units killed hundreds of unarmed Vietnamese civilians at My Lai and nearby hamlets.

The division did not mean that every Americal soldier participated in the massacre. Responsibility centered on particular units and commanders, while helicopter crewmen such as Hugh Thompson Jr., Glenn Andreotta, and Lawrence Colburn intervened to protect civilians. The massacre was initially reported as a successful battle, and investigations were delayed or minimized before later Army inquiries exposed the killings and an associated cover-up. The 101st Airborne, 25th Infantry, and 1st Cavalry divisions were major Vietnam formations, but they were not the division associated with My Lai.