The Prosperan military is a mobile, naval-based fleet, that almost exclusively acts in a peacekeeping way due to the lack of any outside threat. There are three carriers, which are massive dreadnought-type spaceships which essentially carry an entire fleet in their belly. There are a number of battleships as well, which are more adept at planet invasion than actual space combat. Navy and Marines are primarily the ones deployed, while Army tend to be local security on whatever planet one is drafted on.
The Navy is the most important branch of the service. It manages the Prosperan Fleet, commissions and trains officers for command of ships, and maintains frontier guards. The Navy is in charge of the Marines, and a Marine officer can only get so far before being outranked by an Admiral. Enlisted Naval personnel tend to the ship, do office duties, and occasionally go in behind Marines in action. Commissioned Naval personnel command larger ships, fly fighters, manage enlisted personnel, and sometimes help govern colonies. Enlisted serve 8 year terms, while officers serve 20 year terms.
Battle fleets take up various different forms, depending on need. The largest battlefleet is actually self-contained- a single carrier holds an entire fleet, ready to be deployed within a moment's notice.
When a Carrier Fleet is called in, it means that the truest and purest notion of navy doctrine is being unleashed; complete and utter destruction of whatever opposition force is being targeted. During combat, due to how much coordination is needed for managing over 50 warships at once, the Navigator acts as commander and C2 using several AI programs.
The second type of battlefleet is based around a Battleship, essentially planet invasion platforms with light escorts. For major operations, a battleship will set up with a carrier, and true hell will be unleashed upon whatever poor world is targeted. A Battleship will typically be escorted by several dozen Escort Destroyers, slightly less in quality due to requiring a warp drive.
The Marines are a subset of the Navy, but are essentially a branch in and of itself. They serve aboard larger ships, starports, and occasionally on the ground, doing guard duties and customs checks. The Marines are an extremely elite group and go through rigorous training and often do anti-revolutionary and suppression duties in colonies where it’s needed. The Marines also include the elite black ops battalion, The Watchers, who have been known to make entire ships disappear. Due to the dangerous nature of the job, enlisted Marines serve only 4 year terms, while officers serve 20 year terms.
The Army are any military personnel not assigned to a ship or starport. Most Army bases tend to be local and planetside, so Army units going rogue is neither uncommon nor unexpected. While both trained and equipped to a lesser degree than Marines, the Army does peacekeeping duties on whatever particular colony they inhabit, serving 10 year terms.