Reply #21: The Marine Corps is a much more agile force

[Burma Jones]

Other posters have made much the same comment. The Marines operate by means of task forces, called a Marine Air Ground Task Force or MAGTF, which are created very quickly in response to a specific requirement. The entire USMC is geared around organizing, equipping and deploying MAGTFs. Some years ago, Donald Rumsfeld created a stir (and some enemies in the Pentagon) by suggesting that the USMC begin to realign themselves to become a "Sustaining Force" which is counter to over two centuries of USMC doctrine. The Army is designed to be a slower but more permanent occupying force, or Sustaining Force.

In short, the two branches do not accomplish identical goals.