The history of the Marine Corps began when two battalions of Continental Marines were formed on 10 November 1775 in Philadelphia as a service branch of infantry troops capable of fighting both at sea and on shore. In the Pacific theater of World War II the Corps took the lead in a massive campaign of amphibious warfare, advancing from island to island. As of 2022, the USMC has around 177,200 active duty members and some 32,400 personnel in reserve.