Size and mission. Marines are optimized for littoral operations, meaning operations at or near the coastline. They are forward deployed aboard Navy vessels and are rapidly deployable anywhere in the world. They are oriented toward combat missions alone and are not intended to be occupation forces or peacekeepers. The actions of the 1st MarDiv in Iraq were rather interesting because they were used as an Army unit would be. Also, the deployment of Marines to Kandahar was unusual because of the distance away from their ships and Navy support.
The Marines have about 100,000 or so (too lazy to look up the numbers) while the US Army has somewhere around 400,000. The Army also tends to be "heavier" with more armored vehicles and more artillery support than is typical of a Marine unit which embarks from a ship by helicopter or landing craft. Marines also consider themselves to be more elite, but I'm sure there are plenty of units within the Army that would dispute the notion.
One thing that is fairly indisputable, however, is that the Marines have exceptional esprit de corps, and the adage, "Once a Marine, always a Marine" holds true everywhere I have seen. Perhaps I haven't met enough Marines, but I haven't heard them talking about I MEF versus III MEF in the same way you hear the 101st compete with the 82nd. The history of the Marines is not about unit accomplishments but about the CORPS as an entirety. It's an interesting outfit, and I highly respect them. You may not find the most well-educated Marines, but you would be hard pressed to find a more highly motivated and earnest group of troops anywhere.
Originally posted by: Ferocious
Marines are a division of the Navy.
The Men's division.
It's "department" not "division". Same idea, but it sounds better.
