Why does the USMC perform duties which are in the remit of the Army?

Question

In every other country, marines are subordinate to the navy and are used mostly in operations which fall under the remit of the term - seaborne attacks and small scale land operations which needed a quick reaction force. The USMC however, whilst being subordinate to the navy, occasionally performs duties which should be done by the army - occupation, large scale land invasions, air support, etc. They even have their own tanks and aircraft and receive more funding than the armed forces budgets of most states in the world.

Why is this? Wouldn't it be easier for organization and command purposes to absorb most of the land and air assets of the Marines into the Army?

Answer 1

There is a joke passed among the armed services that is an apt description for a possible answer to this question.

There is an office at the pentagon, staffed by a representative of each branch of the military.

The phone rings, and the Army rep answers. "Sir, we have secured the building." He is going to believe that the Army has established a defensive position in the building.

The phone rings, and the Marine rep answers. "Sir, we have secured the building." He is going to believe that the Marines charged a defended position, eliminated the opposition, and is moving to the next objective.

The phone rings, and the Navy rep answers. "Sir, we have secured the building." He is going to believe that the floors have been swept and mopped, and the building is locked for the night.

The phone rings, and the Air Force rep answers. "Sir, we have secured the building." He is going to believe a 3 year lease has been signed, with an option to buy.

Historically, the USMC is employed as a projection of naval power ashore, establish a beach front for the embarkation of additional forces. However, the last 1.5 decades has seen a realignment of that design, because of the unique destructive skills of the Marines during ongoing conflicts.