A beachhead is a temporary line created when a military unit reaches a landing beach by sea and begins to defend the area as other reinforcements arrive. Once a large enough unit is assembled, the invading force can begin advancing inland. The term is sometimes used interchangeably (both correctly and incorrectly) with "bridgehead" and "lodgement". Beachheads were important in many military actions; examples include operations such as "Operation Neptune" during World War II, the Korean War (especially at Inchon), and the Vietnam War.