 Complete the following phrase:  In World War I, battle-tested, veteran Marines served a central role in the United States entry into the conflict. Between the world wars, the Marine Corps was headed by Major General John A. Lejeune, another popular commandant. In World War II, the Marines played a central role, under Admiral Nimitz, in the Pacific War, participating in nearly every significant battle. The Corps also saw its peak growth as it expanded from two brigades to two corps with six divisions, and five air wings with 132 squadrons. During the Battle of Iwo Jima, photographer Joe Rosenthal took the famous photo Raising of the Flag on Iwo Jima of five Marines and one naval corpsman raising a U.S. flag on Mount Suribachi. The Korean War 19501953 saw the 1st Provisional Marine Brigade holding the line at the Battle of Pusan Perimeter, where Marine helicopters VMO-6 flying the HO3S1 helicopter made their combat debut. The Marines also played an important role in the Vietnam War at battles such as Da Nang, Huế, and Khe Sanh. The Marines operated in the northern I Corps regions of South Vietnam and fought both a constant guerilla war against the Viet Cong and an off and on conventional war against North Vietnamese Army regulars. Marines went to Beirut during the 1982 Lebanon War on 24 August. On 23 October 1983, the 