While the Longinius and Achileus armors allowed the FWLM to quickly establish a formidable reputation for armored-infantry operations, a constant criticism of the designs was their lack of heavy-hitting firepower, particularly in light of the growing anti-BattleArmor weapons and designs employed by the League's enemies. Work on a heavier and better-armed combat suit began in 3059 on the eve of the War against Clan Smoke Jaguar but did not bear fruit until 3063, when the first Phalanx prototypes began testing on Irian.
         A succession of problems dogged the Phalanx project ranging from faulty myomer musculature to under-performing and fragile processor suites. The FWLM initially sought to develop the design solo but by early 3062 admitted defeat and sough the assistance of the League's Word of Blake allies. The Blakists' technological savvy quickly dealt with the problems, resulting in a suit that, while not as capable as the Clan model, was nonetheless a first-rate design. The cost of this assistance was the right of the Word of Blake troops stationed in the League and on Terra to utilize the Phalanx in conjunction with their own specialist designs like the Purifier and Tornado.

         Retaining the mobility of its lighter cousins, the Phalanx is surprisingly swift and responsive for its mass, though the presence of the bulky missile pod hinders its agility until jettisoned. The vicious battle claw mounted on the left hand allows the suit to rend opponents, even those protected by 'Mech-grade armor. The right arm is covered by a simple armored glove, giving almost total functionality with that hand. However, the duel FWLM-WOB usage of the design has led to the development of two variants of the Phalanx, one employed by each military. The most common version (usually designated Phalanx-A), laid out in the initial specifications and employed by the FWLM, adds a deadly man-portable King David Light Gauss rifle. The Word of Blake initially used the -A variant too, but later models swap the Light Gauss for the newly developed T-SEMP, resulting in the -B variant of the design that also features additional EMP-hardening of its electronics.

         The Phalanx served well during the Jihad, in both League and Word armies. Many fought each other in fact, on Terra and in numerous other conflicts over the years. The design survived the Jihad in service to the League, and continues to be one of the primary BattleArmors of the member states of that government, though the B variant is relatively rare.