The Vietnam War was a protracted conflict that stemmed from the US policy of containment against communism and fears of the domino effect. It began as US military advisors assisting South Vietnam and escalated to over 500,000 US troops fighting alongside South Vietnamese forces against North Vietnamese and Viet Cong forces. Despite massive US bombing campaigns and troop deployments, the US struggled to defeat the communist insurgency. Growing domestic opposition to the war mounted as casualties rose and victory seemed more elusive. The Tet Offensive of 1968 was a major turning point that turned US public opinion against the war. This led to the withdrawal of US forces and the eventual communist victory in 1975.