Commodore is a rank in some world’s navies for officers above the Captain and below the Admiral. It equates to the North Atlantic Treaty Organization (NATO) rank code 0F-6. It was derived from commandeur, one of the highest positions in orders of knighthood in France. This rank was at first created as a temporary title for Captains who commanded small units or squadrons.
In many navies around the world, the Commodore was regarded merely as a Senior Captain. In the Royal Navy (of Britain), this rank was just introduced to avoid spending too much on appointing more Admirals. In World War II Germany, the Commodore or Kommodore was the rank held by those officers having tactical control over a small squadron of more than one vessel.
In the Canadian Forces and the Royal Navy today, the commodore is the lowest flag officer rank, equivalent to the Brigadier General in the Air Force or the Army. A Canadian or British Commodore is below Major General or Rear Admiral and senior to Colonel or Captain. In the Irish Naval Service, the Commodore is the highest rank and can be held by only one person.
In the United States, the Commodore rank has a complicated history. Like in the Royal Navy, the Commodore in the US Navy was not a higher rank. It was just a temporary assignment for captains. Congress was reluctant to authorize any admirals in service until 1862; thus, considerable importance was given to the position of the commodore. An American commodore was but a captain who was temporarily commanding a small unit of ships for a special purpose. He had no permanent rank and was not recognized by the government.
Today, the US Navy no longer maintains the Commodore rank but the title has survived. Commodores today are senior Captains who are in command of Cruiser, Destroyer or Amphibious Squadrons, Submarine Squadrons, Aircraft Wings, Coastal Warfare Groups and Naval Construction Regiments. These officers are often referred to as Commodore, but they wear the insignia of a Captain.