Imperial Marines

Imperial Marines are some of the finest fighting forces in charted space. They have a reputation for doing the dirtiest jobs against the heaviest odds and prevailing. The primary missions of the Marines are to make initial landings on hostile planets to secure a beachhead, boarding hostile vessels in space and providing forces for enforcing Imperial law, most notably for violations of the Imperial Rules of War. Marines also provide security detachments to Naval vessels and Bases and Imperial installations as needed.
Marines are closely tied to the Imperial Navy. The Navy provides the Marines with the various support activities they require from materiel supply to orbital artillery bombardment. The Navy supplies virtually all of the Marines' administrative support. In return, the Marines provide ship's troops for boarding actions as well as manning ship weapon systems during combat.
Unlike the Imperial Army, the Marines' chain of command comes directly from the Emperor through the Admiralty, and do not fall under command of the local nobility, unless expressly detached for such a purpose. Marines have a tradition that ever Marine is willing and able to fight, from the newest recruit all the way up to the sector marshal.
Selection for the Marines is very strict. Potential recruits must be of average build for their species, be healthy and be capable of fairly strenuous activity. They must not have a criminal history and must be able to submit three references from mature sophonts "of good character". The word of former Marines are very highly regarded.