The 23rd Infantry Division, initially, and more commonly known as, the Americal Division

 The 23rd Infantry Division, initially, and more commonly known as, the Americal Division, of the United States Army was activated 27 May 1942 on the island of New Caledonia. In the immediate emergency following Pearl Harbor, the United States had hurriedly sent three individual regiments to defend New Caledonia against a feared Japanese attack. This division was the only division formed outside of United States territory during World War II (a distinction it would repeat when reformed during the Vietnam War). At the suggestion of a subordinate, the division's commander, Major General Alexander Patch, requested that the new unit be known as the Americal Division—the name being a contraction of "American, New Caledonian Division". This was unusual, as most U.S. divisions are known by a number. After World War II the Americal Division was officially re-designated as the 23rd Infantry Division. However, it was rarely referred to as such, even on official orders.

During the Vietnam War the division had a mixed record. It combined solid service in numerous battles and campaigns with the My Lai massacre, which was committed by a platoon of the division's subordinate 11th Infantry Brigade, led by Lieutenant William Calley.

The Division also had another setback on the early morning of 28 March 1971, Vietcong sapper commandos sneaked into FSB Mary Ann, proceeded to throw explosives and tear gas, knife sleeping soldiers and blowing up key infrastructure delaying rescue. This attack caused 116 casualties leaving 33 killed and 83 wounded.

The division was inactivated following its withdrawal from Vietnam in November 1971.