T-351 Carroway

Designed by Misriah Armory for the UNSC as a main battle tank, the M801 Carroway was created to answer the CMA's need for a tank that can operate in any environment, from the airless tracts of Luna to the bogs of Ballast to the urban sprawls of Gilgamesh. The result was a tank that could traverse any terrain and withstand almost any environmental hazard. Although it was obsolete by 2440, the Carroway saw continual use for another hundred years, almost to the end of the Human-Covenant war.

Role
As an armored vehicle with an innovative layout, the Carroway was the first main battle tank designed for an interstellar war. Once delivered to an operational area by dropship or frigate, it outmaneuvers and destroys enemy armor. It is aided in this mission by its four tracked nacelles, a feature borrowed from vehicle designs meant to cross the Martian barrens. The innovative track and suspension layout allows it to cross terrain that older generations of armored vehicles couldn't touch. This mobility was often exploited to break through enemy lines and run rampant in the rear.

Development
Although primarily an aircraft and small arms manufacturer in the 2300s, Misriah Armories did have a subsidiary that designed and manufactured a few ground vehicles for the Martian market, such as the CM-30 Spider and the CM-260 Offroad Tractor. This subsidiary was the Casteva Martia Corporation.

In 2339, the CMA published a request for a new generation of armored vehicles, among them an MBT. The engineering team at Casteva Martia was finalizing a project to convert Misriah's aircraft design software for use in ground vehicle design. As a proof of concept, the engineers threw together a technical readout for an armored vehicle based on a Martian tractor. The design process took a grand total of twenty-six hours, and the result impressed the Misriah executives enough that they submitted it to the CMA in spite of the fact that Misriah did not have the facilities to manufacture tanks. That's when the trouble began.

The tank (Dubbed the Carroway after an armored cavalry officer in the Rainforest Wars) was by far the least conventional design in the competition. This was a liability, as the aim of the project was to produce a lineup of armored vehicles with extreme parts compatibility. The Carroway performed very poorly in early trials, but the weaknesses were refined, and the original design had a number of strengths. Even though both armor placement and design were suboptimal, the vehicle under the armor was extremely resilient and quick to repair at the depot.

In 2342, General Defense Systems went bust. Two decades of mismanagement drove the company into bankruptcy, and many employees jumped ship. This included engineers who had worked on previous tank designs, and since GDS was too broke to enforce their non-compete contracts, these engineers were able to seek employment elsewhere. A number of them sought out Casteva Martia before Misriah even had the chance to reach out to them. One engineer was quoted as saying "The Carroway project looks like a lot of fun, and I'd hate to miss out."

The expertise brought by these engineers turned the project around. By 2345, the joke entry in the competition was no longer a joke, and was beating out its competitors in most areas of performance. The CMA formally adopted it in 2351, after the requirement for extreme parts compatibility was finally scrapped. By the time of the Inner Colony Wars, the T-351 Carroway was present in such numbers that it served in all but one theater of the ICW.

The UNSC adopted the Carroway as its main battle tank in 2365, under the service name of the M801 Carroway. This name was officially changed to the M801 Wolf Spider when the UNSC standardized on animal names for its vehicles, but the old name stuck in common use until the tank was finally replaced by the M808 Scorpion.

By that time, Misriah had long since been forced to divest Casteva Martia, which functioned as an independent company until being bought up by Chalybs Defense Solutions. The Carroway continued to serve in militias that did not have the money or security agreements with the UNSC to upgrade to the Scorpion. The last of these Carroways were lost by the end of the Human-Covenant War, possibly with the fall of Siberia Prime.

Specifications
The Carroway entered service with a 105mm smoothbore cannon. Although a step down in caliber from previous generations of tank, heavy tanks weren't common in the colonies at the time of adoption, and CMA doctrine called for tank formations to be defeated with aircraft and guided missiles. The Carroway represented the first generational downgrade in armor and armament since the inception of the tank in the first World War. Instead, the gun was designed to maximize ammunition reserves and rate of fire, allowing the tank to fight ferociously or endure prolonged deployments.

As the defense systems available to hostile militias increased in number and potency, the CMA upgunned its Carroways with the M305 120mm smoothbore cannon. The UNSC responded to the same threat by mounting anti-tank guided missile cells on its tanks, reasoning that the M801 Spider's suspension put a hard limit on how potent a gun it could carry. Promising developments in high-velocity cannons would require a heavier chassis, and so the project that would result in the Scorpion was undertaken. In the meantime, ATGMs were mounted as a stop-gap solution.

Secondary weapons were machine guns chambered in thirty and fifty caliber. The UNSC and the CMA experimented with various placements of remotely controlled weapon mounts, and even a few crewed turrets. Eventually, both settled on a "Crow's Nest" atop the turret and a coaxial .50 cal. Special mention should be made of the license-produced Siberian Carroways. Having emerged from a cataclysmic civil war fought in broad ice plains and claustrophobic urban settings, the Siberians designed their Carroways with grenade launchers, flamethrowers, and even minelayers.

Armor was standard titanium composite. Tanks adopted by the UNSC and the CMA also used layers of depleted uranium in the armor. Export rules prohibited colonial governments from purchasing tanks with DU armor, and many militias resorted to rebuilding their Carroways to add that package back in.

T-351 MBT (Adopted as the M801 by the UNSC)
Standard model with the 105mm cannon. Various upgrade packages were made to the sensors and the secondary armament, few of which merited a new model designation.

T-351 S2 MBT (Adopted as the M801B by the UNSC Army)
Model upgraded with a 120mm cannon, improved sensor systems and more comprehensive armor coverage. The M801B eliminated the position of the radio operator, as the UNSC tank doctrine was changing to a three-man crew and moving the fourth man to the depot. The CMA, on the other hand, increased the interface between its tanks and aerial drones. The CMA radio operator became a sensor operator and navigator subordinate to the tank commander.

T-22 Tank
License-produced by Novaya Zemlya OZ during the Decision War. The Siberians made enough changes to the design for it to be considered a distinct variant from the T-351. As the Decision War continued, the Siberians continued to iterate on the design. The model that emerged from the war had a distinctive hexagonal turret with a coaxial 25mm cannon and two separate models of flamethrower, once meant to project napalm and the other meant to guard the tank from close-range attacks.

Also of note is the 'minelayer' added to some T-22s. These dropped tracked mines that could be remotely controlled by the radio operator. These were nominally recon drones that allowed the tanks to keep scouting after their infantry screen was compromised, but carried up to ten kilograms of explosive. To this day, the Siberian phrase "Took a shot to the ass" means "wounded by your own weapon".

T-357 Self-Propelled Howitzer (Adopted as the M315 Prairie Dog by the UNSC Army)
Artillery model with a 155mm cannon. Possibly the single most durable model. Even as the Carroway MBT was being supplanted by the Scorpion or other models of tank, Casteva Martia was still filling orders for the Prairie Dog, and 79,000 such vehicles were manufactured. Countless other Carroways were converted into artillery pieces, though the turret ring was adaptable enough that both tube and missile artillery was fitted to the Carroway chassis.

T-352 Recovery Vehicle
Designed with a reinforced frame and fitted with a crane, this vehicle was used to recover tanks from the battlefield. Less than two hundred were manufactured, and the first fifty suffered from defects in the composition of their typho frames that forced them to be retired early.