Gen Westmoreland died on Monday night from natural causes at a retirement home in Charleston, South Carolina, said his son, James Ripley-Westmoreland.
The jut-jawed officer, who rose through the ranks quickly in Europe during World War II and later became superintendent of the US Military Academy at West Point, contended the US did not lose the conflict in Southeast Asia.
“It’s more accurate to say our country did not fulfil its commitment to South Vietnam,” he said.
He would later say he did not know how history would deal with him.
“They put me over there and they forgot about me. I have no apologies, no regrets. I gave my very best efforts,” he added.
Gen Westmoreland oversaw the introduction of ground troops in South Vietnam and a dramatic increase in the number of troops there.
American support for the war suffered a blow near the end of his tenure when enemy forces attacked cities throughout South Vietnam in what is known as the Tet Offensive in 1968. The US public was stunned the enemy had gained access to the US Embassy in Saigon.
After the event, Westmoreland was recalled to Washington to serve as the US Army Chief of Staff.
Later he led the November 1982 veterans’ march in Washington to dedicate the Vietnam War Memorial.
He called it “one of the most emotional and proudest experiences of my life”.
William Childs Westmoreland was born near Spartanburg, South Carolina, in March 1914, into a banking and textile family.
He is survived by his wife, son and two daughters.