The M113 is a fully tracked armored personnel carrier that has formed the backbone of the United States Army`s mechanized infantry units from the time of its first fielding in Vietnam in April 1962.[2] The M113 was the most widely used armored vehicle of the U.S. Army in the Vietnam War, earning the nickname `Green Dragon` by some people, but largely known as an APC and ACAV (armored cavalry assault vehicle) by the allied forces,[3] as it was used to break through heavy thickets in the midst of the jungle to attack and overrun enemy positions.