Immediately following the Inner Sphere's first contact with Clan BattleArmor in 3050, the militaries of all five Great Houses began intense research to develop and mass-produce their own BattleArmor to counter this new Clan threat. At first, Inner Sphere researchers had no models on which to base their designs, because the Clan forces were sweeping away all who opposed them and leaving virtually no battlefield salvage for Inner Sphere forces. Thus, Inner Sphere designers were forced to reach all the way back to the Star League era, to sketchy records of power armor suits such as the Nighthawk, which was used by scouts and special forces of the original SLDF. Early BattleArmor protoypes based on this data fared poorly in combat simulations and research proceeded slowly at best.
         As the Clans suffered their first few defeats, Inner Sphere forces managed to capture Clan BattleArmor, and Inner Sphere engineers were able to closely examine the new weapon. Soon they had developed copies of the Clan BattleArmor using technology available throughout the Inner Sphere. The earliest examples of these copies were produced by the Federated Commonwealth's New Avalon Institute of Science (NAIS) and were immediately issued to FedCom troops on the Clan front and select elite mercenaries such as the Gray Death Legion for field testing.

         These suits incorporated many of the same systems as the Clan suits, but the limitations of Inner Sphere technology prohibited the BattleArmor from carrying as much armor as Clan suits and from mounting both the SRM launchers and jump jets standard on Clan suits. In response to these limitations, Gray Death Legion engineers immediately began tinkering with the suits and soon produced two distinct variants the Legion continues to use to this day. Other units used the standard NAIS suits. During the same period, engineers from the Draconis Combine, Free Worlds League and Capellan Confederation began to develop BattleArmor suits based on captured Clan armor. All these suits were functionally identical.
         Continuous refinement of the designs and further analysis of captured Clan suits allowed the addition of compact jump jets to the standard Inner Sphere BattleArmor by the time of the Battle of Tukayyid in 3052. However, Inner Sphere technological limits still precluded an Inner Sphere BattleArmor that contained both jump capability and the additional SRM launcher found on Clan Elemental suits. (The Free Worlds League's Longinus, for example, sports a backpack SRM launcher but is too heavy to jump until the missiles are fired and the launcher is jettisoned.)

         The Inner Sphere militaries have further refined the basic BattleArmor design to create what is commonly known as the Genasi, named after the mythical beings descended from Elementals. Suits like the Federated Suns' Cavalier, the Draconis Combine's Raiden, and similar suits used by many Successor States fall into the Genasi family, normally differing only in looks but mounting the same weapons and capabilities of their relations.