Officer

In a military service, a commission is an order from the service's supreme authority, such as its commander-in-chief, authorizing an individual to lawfully hold a military rank, with all the privileges and responsibilities of said rank. A commission usually appoints an individual to hold an officer's rank.

Commissions have long been used by the supreme authorities of military services throughout history to appoint officers. In the United States military, for example, commissions were granted by the President of the United States, who was the US military's Commander-in-Chief.

When an officer is promoted, the commission he/she has for his or her current rank is revoked, and replaced with a commission authorizing him/her for his/her new, higher rank. The same principle applies in a demotion, except that the new commission authorizes the officer for the lower rank he/she is being reduced to.

In the Federation Starfleet, commissions are granted by the President of the Federation, the supreme commander of all Federation Starfleet forces.

In times of conflict, a temporary commission could appoint an officer to command rank to replace an incapacitated or killed commanding officer. Commander William T. Riker, for example, was granted a field commission promoting him to Captain and given command of the USS Enterprise-D when the ship's commanding officer, Captain Jean-Luc Picard, was abducted and assimilated by the Borg during their first attempt to assimilate Earth (TNG: "The Best of Both Worlds", "The Best of Both Worlds, Part II").

In situations where contact with Starfleet is not possible for very extended periods, a commanding officer has the authority to grant commissions to officers under his or her command, or revoke their existing commissions, i.e. he/she has the authority promote or demote his/her officers. Good examples of this are when Captain Kathryn Janeway, commanding officer of the USS Voyager, promoted her Chief Tactical Officer and Security Chief, Lieutenant Tuvok, to the higher rank of Lieutenant Commander, or when she demoted her Flight Controller, Lieutenant Junior Grade Thomas E. Paris, to Ensign. (VOY: "Revulsion", "Thirty Days"). After a year of exemplary service, she re-promoted him to his former rank (VOY: "Unimatrix Zero").