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Thanatos-class heavy battleship
Class Overview





Vindication-class light battleship


39.8 trillion cR


2549 - present




4 (2553)

Technical Specifications




3,683 metres (12,083 ft)


180 million metric tons


2 Boglin Fields' Colossus Mark 3 fusion drives


Kawanishi Engineering's SED-2548NR SFTE (CODEN V equivalent)


RMC's SMR-#8192 Helium-3 fusion reactor


2.9 - 3.5 metres of Titanium-A2 battleplate




1,600 sailors

Additional Information


Human-Covenant War

"We have exhausted all other options - we must stand and fight."
―CPTN Malcolm Marriott, while aboard the UNSC Thanatos

The Thanatos-class heavy battleship (hull classification symbol: BB) is the last model of super-heavy warship developed by the United Nations Space Command during the Human-Covenant War. It is designed to defeat almost any one Covenant capital ship, and with limited support is capable of matching most CAS-class assault carriers. It combines the very best elements of any combat ship that came before, with an advancement on honeycomb bracing, a diverse armament, and one of the most sophisticated fleet management system yet conceived, to allow it to efficiently thrive within heavy combat. Although a potent spatial combatant, it was hampered by a number of weaknesses, not least its speed and costly construction, and so failed to push off the Covenant's advance towards the core worlds.

The Thanatos-class battleship was one of two ships that resulted from Project: OUROBOROS, the other being the famed Infinity-class supercarrier. While the latter was intended to ferry a privileged population away from Human Space, the Thanatos-class was envisioned to be its mighty defender - a vessel that could destroy any Covenant task force that intended to follow them. They first saw action at the Siege of Paris IV, where it performed well at stalling the invasion forces. The few battleships would participate in nearly two dozen engagements during the war, with most of these being in defensive stands above the UEG's most precious worlds. Unfortunately, most of these formidable ships would extremely-short but distinguished service lives, with only a single battleship surviving the war. Although the UNSC has authorised a new batch, as of 2559 they are still undergoing fabrication.

Operational History


"Go ahead and build your new supercarrier, take it and run to wherever the hell you think you’ll go. We’ll build something to defend the Earth, to defend us, not to run away and hide."
―Vice Admiral Michael Stanforth[2]

In the first five years of the Human-Covenant War, the UNSC's efforts at stopping the Covenant's advance had done little to stop the Outer Colonies from being thoroughly overrun. Their onslaught continued to claim worlds by the day, even with the mobilisation of hundreds of ships and a number of flag officers to the region, which forced the UNSC's leaders to begin to question whenever the conflict could be won with their current arsenal. Numerous projects were proposed and accepted, and in 2534 they controversially activated Project: OUROBOROS. Assuming that all attempts would fail in their aim to achieve victory over the Covenant, the project outlined a number of goals that needed to be achieved to ensure the survival of the species, each of which was pursued by one subprogram under the brand, and all being lead by a senior officer of the Office of Naval Intelligence. The two largest groups were codenamed PHOENIX, led by Vice Admiral Elizabeth Sark, and AEGIS, which would be headed by Vice Admiral Michael Stanforth. PHOENIX was responsible for building the ark that would carry the remnants of humanity, while AEGIS would be the shield that protects it. Both ships were intended to be built by the same type of drydock, which would also be handed under another wing of OUROBOROS.

Vice Admiral Michael Stanforth, the head of ONI Section 3, would volunteer himself to lead Project AEGIS.

With support from industrial giants such as Reyes-McLees Shipyards and SinoViet Heavy Machinery, the future battleship was designed by a brilliant design team lead by Doctor Coleman Sterling and Distinguished Naval Engineer Malcolm Contre. It would go through a gruelling nine-year-long development cycle, as lessons learned on the battlefield and those on previous warships, including failed designs such as the Lelantos-class, would be incorporated into an increasingly-complex frame. Such lessons included a general shift towards heavier naval coilguns, thicker and more effective methods of protection, and advanced combat systems. Stanforth's personal support would see a great deal of technology from other classified programs being incorporated, in many cases even before the PHOENIX team were permitted access to it. Indeed, this competition with their peer division would only grow throughout its development, and led to the engineers becoming disillusioned with the idea of relocating humanity from Earth. They believed that it would be best utilised to protect what remains of the colonies, and so they reluctantly accelerated their work and delayed the installation of revolutionary-new components such as energy shielding.

The first two new battleships, which would be christened as the Thanatos and Mars, were first laid down at SinoViet Naval Yard DC-10 above Reach in 2544. A shipyard built specifically for the needs of the upcoming giants, DC-10 accommodated two Special Assembly Plants, as it was planned for only two battleships to enter service. At Stanforth's urging, both hulls would be removed from their berths once they were built up sufficiently enough to allow for groups of smaller drydocks to take over, typically after a period of three years. This freed up the naval yard for the next two vessels, and would become standard practice in order to get as many ships into service as possible. The UNSC Thanatos was finally commissioned on March 4, 2549, with the Mars being completed some months later.

Human-Covenant War

Role & Usage

When compared to other UNSC ships of the time period, the intended use for the Thanatos-class heavy battleship is decidedly simple; to act as a mobile weapons platform that can challenge the Covenant's fearsome capital ships, no matter where that might be. True to this goal, these warships best perform against a couple of large, slow targets, where their batteries of oversized naval coilguns and missiles can best pound away at their hull without fear of being outmanoeuvred. Although each comes standard with a sophisticated flag deck located close to their centre of mass, their tendency to draw an huge amount of punishment means that few admirals use them as their flagships. Instead, they are employed as communication ships, where they directly receive orders from the fleet's command ship and distribute them to all nearby squadrons, overcoming any obstacles that might hinder the coordination of the larger unit. This is vital to their survival, as the few times a battleship has been separated from their unit has almost-always ensured in their destruction. Finally, although to-date no ship has demonstrated this, but the Thanatos-class can act as a terribly-talented planetary bombardment craft. The very same arsenal that has proven to be so talented at defeating other battleships at range can be easily retuned to target military facilities and population centres, with an uncomfortably-high lethality.

Thanatos-class battleships never travel alone, and they are normally accompanied by a squadron of smaller ships that are dedicated to their protection. They are only committed during defensive actions, where there has been enough time to reinforce existing orbital defences, or during significant pushes where speed is not as important as overwhelming power. To make up for this, in combat they are given a degree of autonomy with how they carry out their orders. The UNSC encourages battleship captains to use their weapons to destroy all identified capital ships or, failing that, isolate the hostile fleet so they can be destroyed in a piecemeal fashion.

Weaknesses and Counter-Tactics

"The tactic worked, right up until they used it against us. All it took was a single Covenant armada that beelined for the Odin to overwhelm it. It was a... terrible, horrible sight from the lifeboat, seeing the ship burn as torpedoes and bombers swarmed all over it. It- it shouldn't have been so easy."
―Post-mission recording from Petty Officer Jamin Holland, describing the destruction of the UNSC Odin.

The Thanatos-class heavy battleship, for all its reverence, is one of the more vulnerable warships currently deployed by the UNSC, and exploiting its weaknesses can often lead to a quick execution. In spite of its size and power, these capital ships only have a small selection of anti-aircraft guns to protect themselves from small attack ships. While some have greater numbers installed later on, Covenant strikecraft have proven exceedingly bold in their strafing runs. Most carriers can easily launch enough fighters to simply overwhelm their defences, and it is for this reason that the Thanatos-class are often shadowed by anti-fighter escorts.



Ships of the Line

Name Hull Classification Symbol Commissioned Destroyed Notes
UNSC Thanatos BB-49 March 4, 2549 2552 Lead ship of the class, destroyed during the Siege of Sol.
UNSC Mars BB-50 July 17, 2549 N/A Assigned to the UNSC's 11th Fleet.




  1. The Thanatos-class heavy battleships fielded during the Covenant War never carried NOVA-class devices, as the warhead was still in its early design phase when they launched. Instead, they were only equipped with much lighter nuclear weapons instead.
  2. Credit for the quote goes to the SotP team, which was originally posted here.