Organisation of the UNSC Navy

The '''UNSC Navy's organisation went through a bewildering array of changes, transformations and reorganisations as structures were altered by battle losses or changes in doctrine and force deployment.

Fleets as of 17 October 2552
The UNSC Navy's fleet were continuously reorganised as both its territory and its manpower and hull strength declined. The following represents the UNSC Navy's fleets as they stood following a complete restructuring and redeployment between 2546 and 2548 (prompted by, among other things, the defeat of the crucial inner colony of Miridem). The Navy comprised, aside from ancillary units under central control, six core fleets; four system defence fleets, primarily for defending their base system but situated strategically to enable rapid force deployment to surrounding inner colonies, and two 'rapid reaction' quick response fleets, based at what were then forward-located colonies and operating at two hours' notice to deploy (undertaking offensive missions or counterattacking above UEG colonies). The four defence fleets were homeported at Earth, Reach, Barrow and Carpathia, while the Quick Reaction Fleets were based at New Carthage and Poseidon. Quick Reaction fleets suffered the highest attrition rates of any unit in the entirety of the UNSC Defence Force; the average warship survived just two expeditionary deployments. Neither New Carthage or Poseidon remained in UNSC control by 2552, with the former being glassed just a year after the 6th Fleet took up residence.

First (Home) Fleet
The UNSC Navy's First Fleet, commonly called the Home Fleet, was the oldest continually active unit in the UNSC Navy, having been constituted during the in 2162 (and thus predating the UNSC itself). As its name suggested, the First Fleet was homeported at Earth, Sol, and permanently stationed in the Sol system. Comprising nearly three hundred orbital defence platforms, over three hundred active vessels and more than 450,000 ship- and surface-based personnel, it was also the UNSC Navy's largest fleet. Stationed in defence of the Sol system for the duration of the conflict, the initially token fleet was significantly expanded during the 2530s and 40s once the enormity of the Covenant threat became apparent, and as strategists voiced concerns of the Covenant jumping directly to Earth. The First Fleet's primary mission was defence of Humanity's homeworld, its political and ancestral heart, though as the war inched into the inner colonies, its subunits were increasingly called on to serve elsewhere. The officer in command of the First Fleet was Fleet Admiral Sir Terrence Hood, who flew his flag from the Trafalgar-class carrier UNSC Intrepid. Following Intrepid's destruction, he and his command staff were transferred to the Argus-class carrier UNSC Leander, from where he commanded until personally leading the assault on the Portal from UNSC Forward Unto Dawn (at his own insistence, despite the frigate's unsuitability as a command ship).

The Home Fleet was divided into sixteen distinct squadrons. The 1st and 2nd Home Defence Groups, comprising four battle squadrons each and commanded by a Fleet Admiral, were the core defensive elements. These were supplemented by logistic and transport squadrons (which provided both underway replenishment to the Navy and strategic airlift to the UNSC Army), a high-readiness rapid reaction squadron, the Mars Defence Fleet (in reality a 1st Fleet squadron), and several expeditionary squadrons (which, in addition to Earth's defence, were equipped to deploy to nearby colonies if necessary).


 * 1st- 4th Squadrons- 1st Home Defence Group, 75 ships, Admiral Jackson
 * 5th Squadron- Rapid Reaction squadron (QRF)
 * 6th Squadron- System patrol
 * 7th Squadron- expeditionary squadron, 14 ships
 * 8th Squadron- expeditionary squadron


 * 9th Squadron- logistic squadron, underway replenishment/strategic airlift
 * 10th Squadron- expeditionary squadron
 * 11th Squadron- Mars Defence Fleet
 * 12th-16th Squadrons- 2nd Home Defence Group, 75 ships, Admiral Harper

During the Battle of Earth in October-November 2552, nearly half of the fleet was destroyed and the remainder forced to flee while the Covenant focused their attention on uncovering the Portal. On November 19, as the Covenant activated the Portal during the, an advance force of three Remembrance-class frigates and four squadrons of Longswords led a strike on the Forerunner dreadnought. Following the departure of all Covenant vessels through the Portal, with the intention of activating the Halo Array, UNSC Forward Unto Dawn, UNSC Death's Head and UNSC Aegis Fate led an expeditionary force to the Ark, while the remainder of the fleet reformed in orbit in expectation of a Covenant killing blow.

Order of Battle (ORBAT)
As it stood on 17 October, 2552:


 * UNSC Intrepid (CVB-3), Trafalgar-class command carrier, flagship

Fifth (Quick Reaction) Fleet
Poseidon

Sixth (Quick Reaction) Fleet
Homeported at New Carthage until 2549, then Sol