In November 1775, the Continental Congress commissioned Captain Samuel Nicholas to form five companies of seaborne infantry to defend against British interests in the Bahamas. After a successful ground action resulting in capturing a significant cache of arms and powder at New Providence, the Marines were born. This force continued apace until 1789 at the cessation of the War of Independence.
Looking toward a potential war with France, the U.S. Congress formally created the Marine Corps in 1797. This force was chartered to serve as an infantry arm in support of the Navy's fleet build-up and defend against outside international interests.
In 1805, after a series of sharp, but inconclusive fights against Barbary Pirates in the form of the Pasha of Tripoli, a Marine force trekked overland to subsequently capture the City of Dema Morocco. This event marked the first time that the U.S. flag flew over foreign soil.
The Marine Corps continued it's force protection job throughout the ensuing decades, by mounting significant operations in WWI, WWII Korea, Vietnam, the first Gulf War, and continues to operate in the war on terrorism in Iraq and Afghanistan.
Today's Marine force is entirely integrated with stand-alone ground, aviation and logistical elements available to serve anywhere, anytime at the convenience of the president. As of 2009, about 184,000 Marines were serving in the Marine Corps. A four-year commitment is required.