The distance between Hue and Can is of 665 miles. So that was the distance stretched by the North Vietnamese Army during the Tet Offensive.
The Tet Offensive was a military operation planned by the government of North Vietnam and executed by the North Vietnamese Army and the Viet Cong in 1968, against the US-led allies, especially the Army of the Republic of Vietnam, during the Vietnam War.
The large number of US soldiers killed during the offensive, about 14,000, was not digested by the American people. The rejection of the war in the United States increased and this meant a turn from the war towards the defeat of the coalition. It is considered to be a strategic victory due to the subsequent change that it caused in the US military strategy.