What officially ended the vietnam war?

President Richard M. Nixon assumed responsibility for the Vietnam War as he swore the oath of office on January 20, 1969. He knew that ending this war honorably was essential to his success in the presidency. He expected that the American people would give him a year to end U.S. involvement in the war, and he expected to succeed during that time—believing that his experience in foreign relations, his toughness, and his willingness to bring to bear military and political pressure on North Vietnam would yield a settlement in the public negotiations just opening in Paris.

Are their any multiple answer's ?