United Nations Marine Corps
The ground and boarding arm of the United Nations Navy.
Marines are the ground and boarding arm of the United Nations Navy. They serve on Earth as military police and guards, make up the troop complement aboard UNN warships, and garrison the UN's protectorates out in the Belt and the outer planets. They fight in powered armor that is vacuum-rated and shielded against radiation, so they can work anywhere a ship can carry them; specialist units wear Reaver armor and the rest use standard UN light armor. The corps can put something on the order of a hundred million troops across the system at one time, far more than anyone else fields, and its people carry the advantage of having been raised in a full gravity.
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