The Vietnam War was a war fought between 1955 and 1975 on the ground in South Vietnam and bordering areas of Cambodia and Laos ("see" Secret War) and in the strategic bombing ("see" Operation Rolling Thunder) of North Vietnam. American advisors came in the late 1950s to help the RVN (Republic of Vietnam) combat Communist insurgents known as "Viet Cong." Major American military involvement began in 1964, after Congress provided President Lyndon B. Johnson with blanket approval for presidential use of force in the Gulf of Tonkin Resolution.