The Navy and the Marines are separate branches of the U.S. military. The Navy deals with control of the seas through attack, defense and transport of military equipment. The original purpose of the Marines was to capture and control "beach heads," but it expanded to involve more ground combat operations.
The Navy and the Marines were both established in 1775. The Marines were part of the Navy at that time and considered the Navy's ground force. In 1798, the Marines were established as a separate branch of the military. Navy ships attack targets on both the land and in the water. The Navy supports the Air Force by providing runways at sea and transporting air craft. The Navy transports Marines on certain missions.
The Marines are the second smallest branch of the military. Only the Coast Guard has less members. There are approximately 153,000 Marines on active duty. The Navy has approximately 324,000 members on active duty. The Marines specialize in fast deployment due to the smaller size of the unit. The Marines do not have any medics or nurses, instead using Navy medics. The Marines have their own air equipment, including fighters and helicopters. Neither the Navy nor the Marines have a National Guard.