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.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,
as it was used to break through heavy thickets in the
midst of the jungle to attack and overrun enemy positions.