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 (such as prowlers), 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). 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.

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).

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

UNSC First (Home Fleet), Sol system, 306 vessels and 300 orbital platforms, Fleet Admiral Sir Terrence Hood commanding


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


 * 1st- 4th Squadrons- 1st Home Defence Group, 76 ships, Admiral Jackson
 * 3 carriers
 * UNSC Avon (CVG-22), Argus-class carrier
 * UNSC Dido (CVG-41), Argus-class carrier
 * UNSC Leander (CVG-42), Argus-class carrier
 * 7 cruisers
 * UNSC Absolution (CG-301), Marathon-class cruiser
 * UNSC Challenger (CG-291), Marathon-class cruiser
 * UNSC Bunker Hill (CG-370), Marathon-class cruiser
 * UNSC Hastings (CG-172), Marathon-class cruiser
 * UNSC Wyvern (CG-233), Marathon-class cruiser
 * UNSC Phoenix (C-511),
 * UNSC Mercator (C-590), Halcyon-class light cruiser
 * 46 frigates
 * (FFG-142),
 * UNSC Resurgence (FFG-3014), Remembrance-class frigate
 * UNSC Reliant Warrior (FFG-2919), Remembrance-class frigate
 * 20 destroyers
 * UNSC Silvercrest (DD-106),
 * UNSC Athena (DD-114), ''Pioneer-class destroyer
 * UNSC Cypria' (DD-240), Pioneer-class destroyer
 * UNSC Llanover (DD-608), Pioneer-class destroyer
 * UNSC Neptune (DD-985), Pioneer-class destroyer
 * DD-336, Hope-class destroyer
 * DD-337, Hope-class destroyer
 * DD-338, Hope-class destroyer
 * 5th Squadron- Rapid Reaction squadron (QRF), 25 ships
 * 4 cruisers
 * UNSC Woodward (CG-411), Marathon-class cruiser
 * UNSC Swordsman (CG-400), Marathon-class cruiser
 * UNSC Aberdeen (CG-246), Marathon-class cruiser
 * UNSC Spartan (C-702), Halcyon-class light cruiser
 * 21 destroyers
 * UNSC Poseidon (DD-609), Pioneer-class destroyer
 * UNSC Sceptre (DD-711), Pioneer-class destroyer
 * UNSC Dragon (DDG-528), Vengeance-class destroyer
 * UNSC Warsaw (DDG-534), Vengeance-class destroyer
 * UNSC Conviction (DDG-535), Vengeance-class destroyer
 * 6th Squadron- System patrol, 30 ships
 * 17 corvettes
 * 12 frigates
 * UNSC Reunion (FFG-3013), Remembrance-class frigate
 * 7th Squadron- expeditionary squadron, 17 ships
 * 1 carrier
 * UNSC Arethusa (CVG-46), Argus-class carrier
 * 9 frigates
 * UNSC Forward Unto Dawn (FFG-201), Remembrance-class frigate
 * UNSC Aegis Fate (FFG-307), Remembrance-class frigate
 * UNSC Paris (FFG-2406), Remembrance-class frigate
 * UNSC Redoubtable (FFG-3016), Remembrance-class frigate
 * 7 destroyers
 * UNSC Ballymena (DD-1003), Pioneer-class destroyer
 * UNSC Spirit of Miridem (DD-1860), Pioneer-class destroyer
 * UNSC Falconer (DD-1868), Pioneer-class destroyer
 * DD-339, Hope-class destroyer
 * DD-340, Hope-class destroyer


 * 8th Squadron- expeditionary squadron, 24 ships
 * 1 carrier
 * UNSC Minerva (CVG-72), Argus-class carrier
 * 1 cruiser
 * UNSC Bristol (CG-402), Marathon-class cruiser
 * 12 frigates
 * 10 destroyers
 * UNSC Destiny's Child (DDG-544), Vengeance-class destroyer
 * UNSC Drake (DDG-545), Vengeance-class destroyer
 * 9th Squadron- logistic squadron, underway replenishment/strategic airlift, 35 ships
 * 10th Squadron- orbital defence platforms, 300 stations
 * 11th Squadron- Mars Defence Fleet, 23 ships
 * 1 carrier
 * UNSC Aesop (CVG-45), Argus-class carrier
 * 3 cruisers
 * UNSC Iron Warrior (CG-403), Marathon-class cruiser
 * UNSC Orion (CG-440), Marathon-class cruiser
 * UNSC Pass of Ballater (C-708), Halcyon-class light cruiser
 * 13 frigates
 * (FFG-2011), Remembrance-class frigate
 * UNSC Foxhound (FFG-2789), Remembrance-class frigate
 * 6 destroyers
 * 12th-16th Squadrons- 2nd Home Defence Group, 75 ships, Admiral Harper
 * 3 carriers
 * UNSC Arlington (CVG-23), Argus-class carrier
 * UNSC Argus (CVG-10), Argus-class carrier
 * UNSC Avenger (CVG-43), Argus-class carrier
 * 11 cruisers
 * UNSC Endeavour (CG-190), Marathon-class cruiser
 * UNSC Montrose (CG-317), Marathon-class cruiser
 * (CG-), Marathon-class cruiser
 * (CG-377), Marathon-class cruiser
 * UNSC Apollo (CG-379), Marathon-class cruiser
 * UNSC Rambler (CG-386), Marathon-class cruiser
 * UNSC Triumph (CG-390), Marathon-class cruiser
 * UNSC Sleipner (CG-427), Marathon-class cruiser
 * UNSC Defiant (CG-442), Marathon-class cruiser
 * UNSC Councillor (C-677), Halcyon-class light cruiser
 * UNSC Halifax (C-681), Halcyon-class light cruiser
 * 37 frigates
 * UNSC Mother of Invention (FFG-636), Remembrance-class frigate
 * UNSC Death's Head (FFG-2714), Remembrance-class frigate
 * UNSC Revelation (FFG-3015), Remembrance-class frigate
 * 24 destroyers
 * UNSC Dunedin (DD-611), Pioneer-class destroyer
 * UNSC Huntsman (DD-859), Pioneer-class destroyer
 * UNSC Sheffield (DDG-522), Vengeance-class destroyer

Second (Epsilon Eridani) Fleet
152 vessels and 20 armed orbital stations as of July 1, 2552 (under construction vessels discounted). Destroyed at the in August 2552; surviving ships (examples Leander, Sheffield, Aegis Fate) amalgamated with the 6th QRF at its new base in Barrow.

ORBAT
As it stood on July 1, 2552:
 * UNSC Trafalgar (CVB-1), Trafalgar-class carrier
 * (CVG-28), Atlas-class carrier
 * (CG-280), Marathon-class cruiser
 * (CG-295), Marathon-class cruiser
 * UNSC Swiftsure (CG-389), Marathon-class cruiser
 * (C-709),
 * (C-711), Halcyon-class cruiser
 * (FFG-1547). Remembrance-class frigate
 * (FFG-1729), Remembrance-class frigate
 * UNSC Resurgence (FFG-3014), Remembrance-class frigate
 * UNSC Restless (FFG-3061), Remembrance-class frigate
 * UNSC Aegis Fate (FFG-307), Remembrance-class frigate
 * UNSC Gettysburg (FFG-2011), Remembrance-class frigate
 * (FFG-318),
 * (FFG-371), Paris-class frigate
 * (FFG-372), Paris-class frigate
 * (FFG-1372), Stalwart-class frigate
 * (DD-431),
 * (DD-216), Pioneer-class destroyer
 * (DD-401), Pioneer-class destroyer
 * (DD-7430), Pioneer-class destroyer
 * UNSC Vengeance (DDG-521), Vengeance-class destroyer
 * (DDG-523), Vengeance-class destroyer
 * UNSC Final Effort (DDG-524), Vengeance-class destroyer
 * UNSC Valiant (DDG-529), Vengeance-class destroyer
 * UNSC Fateful Journey (DDG-530), Vengeance-class destroyer
 * UNSC Final Charge (DDG-532), Vengeance-class destroyer
 * UNSC Out of the Past (DDG-537), Vengeance-class destroyer
 * DD-347, Hope-class destroyer
 * DD-348, Hope-class destroyer
 * DD-349, Hope-class destroyer
 * DD-350, Hope-class destroyer
 * DD-351, Hope-class destroyer
 * DD-352, Hope-class destroyer
 * DD-353, Hope-class destroyer

Third (Barrow) Fleet
Survived the war largely intact. UNSC Fortitude (CVB-4) was based here (though not technically as part of the Third Fleet) as the fleet's 'ready reserve carrier'. Barrow hosted the reformed 6th QRF after the destruction of New Carthage, with Fortitude becoming flagship.

ORBAT

 * UNSC Hermes (CBG-75),
 * UNSC Northwood (CG-289), Marathon-class cruiser
 * UNSC Radiant (FFG-3428), Remembrance-class frigate
 * UNSC Starlit Sky (DDG-527), Vengeance-class destroyer
 * UNSC Courageous (DDG-533), Vengeance-class destroyer

Fifth (Quick Reaction) Fleet
Poseidon

Sixth (Quick Reaction) Fleet
The Sixth (Quick Reaction) Fleet was based above the vital inner colony of New Carthage, until its destruction during the Battle of New Carthage in November-December 2549. Following its severe depletion in defending its own home port, the 6th Fleet was based above Barrow, where UNSC Fortitude, the fleet reserve carrier, replaced Vanguard as 6th QRF flagship following the latter's damage. Here the 6th QRF was replenished with vessels and crew from shipyards above Reach, Mars and Barrow itself. Following the Fall of Reach, with the increased threat against Earth (and the absorption of the Second Fleet's undamaged vessels to the 6th Fleet), a significant portion of the 6th Fleet was transferred to the Home Fleet. As soon as word of the attack on Earth was received, the 6th QRF deployed to Earth and arrived on January 9, 2553, too late to participate in the battle. The fleet remained in Sol for the next four year, with Fortitude, the sole intact command carrier, taking over as flagship.

ORBAT
As of November 1, 2549, New Carthage:


 * UNSC Vanguard (CVB-2), Trafalgar-class carrier
 * UNSC Absolution (CG-301), Marathon-class cruiser
 * UNSC Warsaw (DDG-534), Vengeance-class destroyer
 * UNSC Obliterator (DDG-536). Vengeance-class destroyer
 * (FFG-209), Stalwart-class frigate

As of August 17, 2552, Barrow:
 * UNSC Fortitude (CVB-4), Trafalgar-class carrier
 * UNSC Relentless (FFG-3217)