The Prosperan Republic Interstellar Marines (PRIN) is a subsection of the Prosperan Navy responsible for providing power projection from carriers and space, using the flexibility of the Prosperan Navy to rapidly deliver combined-arms combat specialists.
The Marines have been a component of the Prosperan Navy since the first colonies were founded. The Army was unsuited to space warfare, and only a small section of the Army was trained in the specialized tactics required to effectively commit to boarding parties, boarding defenses, planetary invasions, and zero-g combat. The Marines were founded by the division of this brigade, and evolved into becoming the primary combat force of the Navy, eventually diminishing the role of the Army into primarily garrisons and self-defense forces.
The Marines have around 300,000 members active on carriers, 1.2 million members on cruisers and space stations, and just under 400,000 reservist Marines.
The Watchers are a subset of the Marines, the elite of the elite. They are a special forces brigade that excels in black ops and in 'go silent' operations. In particularly dangerous operations, The Watchers are called in to settle the situation effectively and silently.