The Geneva Agreement of 1954 divided Vietnam at the 17th parallel into communist-backed North Vietnam and U.S.-backed South Vietnam. American military aid and advisors began arriving in South Vietnam two years later. President John F. Kennedy sent the first American combat troops to Vietnam, and President Lyndon Johnson expanded U.S. involvement to the level of war. In 1965, 25,000 American soldiers committed in Southeast Asia grew to 543,000 U.S. troops in country by 1968. The communist Tet Offensive in 1968 offset advantages gained and turned the tide against the south. U.S. intervention in Vietnam became the focus of protests across America and the world in the late 1960s. Elected in 1968 on a promise to withdraw American troops, President Richard Nixon fulfilled that pledge by 1973, when the last U.S. troops departed Saigon by helicopter under a temporary cease-fire agreement that he called "Peace with Honor." Without American combat support, South Vietnam was eventually overrun by northern forces, leading to the fall of Saigon in 1975 and the official end of the Vietnam War.