The XM58 was a prototype armored fighting vehicle mounting a large laser weapon intended to be used as tank destroyer, direct fire artillery piece, and assault gun, consisting of a Mark XI super heavy laser weapon, the same design mounted on the Liberty Prime robot.
After the announcement of General Constantine Chase's announcment of the Liberty Prime robot project, a cadre of high-ranking military officers lead by General John Moretti (who previously headed the P94 plasma rifle replacement committee as a colonel), who described the robot as "too expensive for mass production". Moretti also pointed out that, while heavily armored, the robot was far from invincible, and it's lack of anti-air armament made it vulnerable to high altitude aerial attack. Moretti also noted that the bipedal design of Liberty Prime contained inherent weaknesses, namely the joints which, in spite of the best efforts of the design team, could not be made completely impervious to attack.
In addition to his criticisms, Moretti and his design team submitted plans for an armored vehicle on the chassis of the M49 Heavy Tank armed with the same high-powered laser cannon as the Liberty Prime robot. This design, unlike the robot, could be mass produced in large numbers, while possessing all of the firepower of Prime's main weapon.
After hearing both proposals, it was decided that both projects would be approved, with Liberty Prime being constructed primary as a propaganda tool and for "shock and awe", while Moretti's design, designated XM58 Self-Propelled Laser Weapon, would be slated for testing and mass production.
The XM58's chassis is identical to that of the M49 heavy tank, mounted on two separate tracks. The rear of the tank is taken up by a massive nuclear reactor, which rises above the rear of the vehicle. Because of this, the turret can only rotate about 180 degrees, however, as the vehicle was intended to fire from long ranges, this was deemed acceptable.
The turret itself mounts the focusing array, sometimes referred to as the "barrel", for the laser weapon, looking similar to a massive laser rifle focusing array. The array contains a series of lenses and mechanisms for adjusting the focus of the beam to impart maximum energy at all ranges. The focusing array is surrounded by a cooling shroud containing cryogenic fluid. The turret also mounts a remote weapons station for a .50 caliber machine gun or Gatling laser to defend the vehicle should it come under infantry attack.
The crew of two men, a gunner and driver are seated in side-by-side in the front hull of the vehicle. The gunner aims the main armament using a joystick and a full-color monitor, and fires using a trigger mounted on a joystick. The control surfaces also allow the gunner may set the power output and focusing of the laser. Since the weapon uses a laser beam rather than a solid projectile, once the power and focusing are set, the gunner need simply place the crosshair over the target on screen and fire. The weapon can only miss due to human error, though atmospheric conditions may interfere with the beam. A fire control computer produced by RobCo can be set to automatically track and engage faster-moving targets, such as aircraft once the gunner has selected the target.
Two XM58 prototypes remained at the Nevada Test Site, protected from the Great War in a bunker and kept relatively intact because of the dry climate of the region and cool temperatures in the underground bunker. They would remain there until 2281, when the New California Republic military recovered the two prototypes and brought them into active service.
Siege of KingmanEdit
After the NCR victory at the Second Battle of Hoover Dam, the XM58s were deployed as part of the northern force of the three-pronged attack on the Legion-held city of Kingman, Arizona. During the early stages of the Siege of Kingman, the Third Caesar Aurelius ordered a force of several dozen improvised fighting vehicles, a few pre-war tanks and APCs, and about two centuries (~200 men) to attack the northern NCR and allied (Also including New Vegas, Brotherhood, Boomer, and Enclave Remnant forces) force near Dolan Springs, Arizona, in what would become known as the Battle of Dolan Springs. The XM58 would see its first combat in the battle, where the two vehicles performed outstandingly, destroying five Legion tanks and 27 improvised vehicles between them. Along with armored forces and mechanized infantry- sent fresh from the NCR to support the offensive, the NCR forces destroyed what most of what little armor the Legion had. Following the victory at Dolan Springs, the two XM58s were placed in along an old gravel road through the Cerbat Mountains to the west of Kingman, in a position where they could fire down on the city. The XM58s were used for as precision artillery, firing over 150 times during the course of the battle on Legion artillery batteries, supply caches, and fortified buildings. In this role, the XM58 proved just as deadly as it did in and anti-armor role, with the beam easily detonating stockpiled munitions and burning through steel support beams, sending buildings collapsing into a pile of burning debris.
Siege of Nova RomaEdit
During the Siege of Nova Roma, the NCR deployed the XM58 SPLWs along with the rest of their armor, placing the vehicles in a position where they could fire on distant targets and cover the NCR forces from a range. During an engagement at the crossroads of Interstates 40 and 17, the two XM58s together destroyed at least six Legion vehicles and sixteen defensive positions. The vehicles were also present at the engagement where Aurelius of Phoenix was killed. While Aurelius' vehicle was destroyed by conventional tank gun fire, the XM58s did knock out six of the last remaining Legion pre-war fighting vehicles in the city, and discharged three pulses into the advancing Legion infantry, vaporizing dozens of Legionaries.
Siege of SedonaEdit
While seeing little action in the rugged terrain of the Battle of Oak Creek Canyon, the XM58s were deployed in the latter stages of the the conflict, placed on the Mogollon Rim in a position where they could fire down on the city. There, they provided precision fire support in a similar manner to how they were deployed in the Siege of Kingman, firing over 100 fire missions, typically targeting Legion fortifications.