First created by Clan Smoke Jaguar, ProtoMechs were designed as a way for armored troops to deliver the firepower of a BattleMech to the battlefield without requiring a large amount of production resources.
In the months after the Battle of Tukayyid, Clan Smoke Jaguar found themselves with a serious problem. Guerrilla raids and uprisings within their Inner Sphere occupation zone had left them stretched to the limit in resources. Smoke Jaguar scientists found that if something wasn't done soon, their Clan worlds would soon be stripped of the ores needed for BattleMech production.
The Clan's top scientists went to work on a radically different battlefield unit design that would combine elements of BattleMechs and that of Elemental Battle Armor. Standing only half the height of a BattleMech, the smaller units would mass only one-tenth that of the larger machines. This, combined with their smaller engines, would allow the Smoke Jaguars to make many more of these for less material. Dubbed ProtoMechs, the ultimate goal of these machines was for a Point of five, working in unison, to be as effective as a BattleMech, while requiring less than half the amount of construction resources. At the same time, Smoke Jaguar geneticists began the task of creating a suitable breed of pilot. Unlike the bulky Elementals, this new breed would need to be smaller even than Aerospace pilots, so that they would be able to fit into the cramped confines of a ProtoMech's torso. Knowing that their Khans would not even consider full-scale production of ProtoMechs until they were proven effective in combat, the Smoke Jaguar scientists and geneticists began working on the project in secret, understanding that it could be years before their work could be revealed.
It was not until the development of the Enhanced Imaging (EI) system by Clan scientists that the ProtoMech concept became a viable one. The EI control system laid the groundwork needed by Smoke Jaguar scientists for controlling the ProtoMech. The ability to give the pilot direct neural control eliminated the need for a gyroscope and full-sized cockpit. This gave room for the pilot to ride in the torso while still allowing ample space for weapons. However, the problem of breeding suitable pilots was harder to overcome. The failure of their breeding program left the Smoke Jaguars no one but volunteer Aerospace pilots who had failed to test into the Warrior Caste.
After the Great Refusal and the destruction of the Smoke Jaguars, ProtoMech technology was acquired by Clan Coyote and Clan Blood Spirit who are one of the few Clans to actively pursue development of this combat unit. Research by the Blood Spirits and Clan Snow Raven led to the development of post-Refusal ProtoMechs such as the Chrysaor and Cecerops. However the concept is still meeting resistance from the warriors of the Clans, even those that actively develop ProtoMechs.
The Inner Sphere has not begun any ProtoMech research that is known of; their first encounter with these units was during the campaign against the Smoke Jaguars. For the current time at least, ProtoMechs are a Clan-exclusive technology.
ProtoMechs weigh two to nine tons and stand on two legs anywhere from four to six meters in height. With their fusion engines, they can move considerably faster than battle armor but are more compact than BattleMechs. As such their ability to navigate terrain falls somewhere between infantry and 'Mechs.
Like battle armor and BattleMechs, ProtoMechs such as the Roc can mount jump jets which further increases maneuverability. ProtoMech armor is more efficient in terms of its weight-to-protection ratio compared to 'Mech armor due to the reduced surface areas involved. The heaviest ProtoMechs can boast almost as much protection as some light 'Mechs.
Due to their size and tonnage, ProtoMech weapon loadouts are somewhere between that of battle armor and 'Mechs. Weapons such as the ER Micro Laser and Light Machine Gun were initially developed by the Smoke Jaguars for ProtoMechs, though they have since spread to other combat units. The Light Active Probe was also developed for ProtoMech usage. Equipment appears to be fixed for the most part, as ProtoMechs do not feature any of the modular systems utilized by OmniMechs and battle armor.
Like other units, the individual ProtoMech designs have their own roles which are determined by speed, armor, and equipment. Some, like the Siren, use their high speed for recon work. Others like the Gorgon can provide fire support, though not to the same degree that heavier vehicles can.
 First Generation ProtoMechs
 Second Generation ProtoMechs
 Later Designs