The commission of Brevet was accorded to officers who had been appointed to serve as a military officer in a—usually higher and often temporary—rank without a confirmed promotion to the specified rank.
On a mission to Haruun Kal during the Clone Wars, Mace Windu used his authority as a Jedi General to both swear Nick Rostu into the Grand Army of the Republic and award him a brevet rank of major. In the aftermath of the Battle of Haruun Kal, Windu recommended Rostu's rank be made permanent.
As a lieutenant with the New Republic, Myn Donos rose rapidly through starfighter pilot training and was given command of Talon Squadron upon graduation, with the brevet rank of captain over the training squadron. The rank was removed when he was reassigned after the loss of his squadron at the Ambush at Gravan Seven.
The only Brevet Admiral specifically known by that title was Glie'oleg Kru, who commanded the Bothan Assault Cruiser Champion until its destruction during the Battle of Kalarba, early in the Yuuzhan Vong invasion. However, it appears that a similar position had also been used by the Imperial Navy, as Michael Unther had been the Admiral of a Sector Fleet prior to his promotion to the rank of Rear Admiral, which was almost certainly the lowest substantive flag rank in the hierarchy.
Under both the New Order and the New Republic, these brevet ranks were used when it was necessary to rapidly create new squadrons and local commands; under the New Order, such promotions may also have served to even out the inequalities within Sector Group command structure, since it would have been somewhat absurd for every backwater sector with only a couple of Star Destroyers to be accorded the same amount of senior Naval commanders as more significant Sectors where even third-tier subordinate commands were larger.
- The Complete Star Wars Encyclopedia