Even when forgotten, the Starfleet Marine Corps is always hard at work upholding the ideals of the Federation while guarding it from any adversary that may present itself. In true military fashion, officers of the SFMC place the lives of others before their own, ready to sacrifice anything for their government.

Marines are carried aboard Starfleet ships, but they have their own commanders and are separate from the regular shipboard chain of command. Twenty-fourth century technology, and particularly Holodeck technology, have made it possible to give rank-and-file soldiers the kind of intensive military training that was the sole preserve of special forces units a mere four centuries before. Starfleet Marines are exceptionally well trained and capable, even by Starfleet standards. They are meant to operate primarily on planetary surfaces, both land and water, but are also trained to participate in space-based operations as well. Their skills reflect the fact that they frequently have to operate in a long-range reconnaissance fashion, often with little or no support from Starfleet.

Unlike Naval personnel, Starfleet Marines must meet exacting physical criteria. They are particularly expected to display above-average intelligence and exceptional endurance.

The first difference between the naval and marine branches of Starfleet that one notices is the rank system. Carried down from generation to generation, the system resembles quite closely the ranking method used in 20th century Earth. The next difference is the militaristic nature of the corps. While the Starfleet navy tends to maintain order in a loose but firm manner, some have called the Marine Corps' management technique stringent or even harsh. Quite simply, Marine commanders do not tolerate anything less than the absolute best in their men, knowing that to do so would risk the lives of others. There is little room for error in such a dangerous and important field.