US Army vs. US Marine Corps

What is the difference between the US Army and the US Marines?

The United States has three armed forces under the direction of the Department of Defense: the US Army, US Air Force, and US Navy. The US Marine Corps are actually a branch of the Navy, while the Coast Guard, the other armed force of the United States, is technically under the wing of the Department of Homeland Security. Each branch of the armed services in America performs a vital role for national security.

The US Army and the US Marines are two very different services. The mission goals for each service are different, and they accomplish their work in different ways. While people might be tempted to lump the two together since they both form parts of ground-based invading forces, most Marines would resent implication that the two forces are indistinguishable.

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The US Marines are a highly mobile amphibious attack force. Marines are trained to attack from the water and establish a beach head, an area of control on foreign soil. After the Marines take territory, other armed forces such as the US Army move in to maintain control, while the Marines move on. Marines are mobile, lightweight, and very rapid. One might compare the Marines to the head of a spear, wedging in to get a foothold and racing ahead once the land has been secured.
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In addition to acting as a lightweight attack force from the ocean, Marines are also perfectly capable of taking territory on land. Marines are trained for rapid deployment, and are often the first US military personnel on site. Marines also guard American embassies overseas, providing embassy security and safety. In volatile areas, being a Marine embassy guard is a very risky job.

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The US Army, on the other hand, is the primary ground-based military force. As such, the US Army captures and holds territory with the use of infantry, aircraft, and an extensive support staff. The US Army is in the thick of battle, and is a substantially larger armed force than the Marines. Certain members of the US Army, such as the Army Rangers, have training which is similar to that received by the Marines.
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Both forces have reserve troops, which can be activated in times of need. The Army reserves are significantly larger, however. Unlike the Marines, the US Army also has extensive support staff, including medical personnel. The Marine Corps relies on the Navy for many support services, keeping the service small and efficient.