The construction of the first space colonies in 2045 quickly became a massive project far beyond anything ever attempted before in Earth's history. The project was complicated by the fact that most of the current construction machinery available at the time was not equal to the task of large scale construction in space. In order to increase the production of space colonies EFG engineers began experimenting with new machines for construction. The engineers opted to try and design an all-purpose mecha that could be used in all aspects of colony construction. They eventually came to the conclusion that the only form truly suited to all-purpose construction was the human form. However, since humans were not suited for heavy construction in space, the engineers had to come up with some way of increasing the strength and endurance of a human while maintaining the dexterity. Eventually they came up with the Hydro-Skeleton, or HS; a large exoskeleton with maneuvering thrusters that could be worn over the standard space suit. The Hydro-Skeleton was a fantastic success, increasing the work output of the construction personnel by over 500%.
Over the years the design of the Hydro-Skeleton developed considerably. The original design developed into a robot unit with an enclosed cockpit for the pilot. Advanced computer control took over the repetitive and mundane functions of the suit, allowing the pilot to concentrate on more detailed matters of construction. Eventually the Hydro-Skeleton evolved into what is now called the Junior Mobile Suit (JMS). JMS units are not used much in modern times except for colony maintenance and asteroid mining, and occasionally for training of Mobile Suit pilots. Although some engineers had experimented with large scale Hydro-Skeletons for heavy construction, they were never able to perfect a power source that was both powerful enough to supply the needs of a large suit, but small enough to actually fit in the aforementioned suit. This problem was inadvertently solved by the discovery of the Minovski particle.
In U.C. 0070 a physicist named Dr. Minovski discovered a new particle that could absorb large amounts of electromagnetic radiation. Scientists quickly realized that this particle, named the Minovski particle, could be put to use in two ways. First, Minovski particles could be used to produce materials that would screen out most forms of radiation. This meant that shielding for nuclear reactors could be made extremely small while still providing full protection for the pilot. Further research in Minovski reactors also led to the discovery of nuclear fusion reactors, which further increased the power output of the small reactors. Second, the Minovski particles could be liberally distributed in an area of space, blocking almost all electromagnetic radiation in the area. This meant that any radar or radio communications in the area would be useless.
The Jion Archduchy was quick to realize the military applications of the Minovski particle. The elimination of radio and radar meant that space combat would soon be limited to visual range only, so the Jion engineers concentrated on developing a fast attack craft that could quickly approach a target and destroy it before the target could visually lock onto the craft. The Earth Federation Military (EMF; the military arm of the EFG) on the other hand started to refit all of their space cruisers with Minovski reactors, hoping to make them much more powerful than their Jion counterparts. This led to the EMF Salamis and Magellan class space battle cruisers, which were the most powerful warships in existence for their time.
The Jion engineers used the Hydro-Skeleton as a basis for their attack craft. They made the suit larger, with heavy armor and a small but powerful Minovski reactor. This new type of vehicle was named the Mobile Suit, or MS. A heavily shielded visual sensor system called the "Mono-eye sensor" was developed and equipped on the MS, giving the pilot a highly-detailed 270-degree view of his surroundings. A hand-held autocannon which was powerful enough to blast through most forms of EMF armor was also developed for the MS. Finally, a powerful system of thrusters was added to the suit to give it high speed and mobility. In U.C. 0074, the Jion military forces unveiled the first successful prototype combat MS, the MS-05 Zaku. By U.C. 0078 all of the initial design problems had been solved, and the Jion Archduchy began mass production of the MS-06 Zaku II, an upgraded version of the original Zaku.  Along with the perfction of the Minovsky reactor scientists found that a ramdom proton was produced.  This lead to beam wepons where many of these particels were released in 1 concerntrated beam, much like a cutting laser.  The perincipality of Zeon chose to ignore this till the ends of the One Year War.  The earth federation, on the other hand, with the V Project underway began to develop these beam guns and sabers, which are small I-fields produced from a sword hilt-like base filled with plasma, very similar to a plasma cutter.  With the EFG's development of beam wepons the Preinipality of Zeon began to develop "mega particel cannons" which we basically a beam rifle only built into the MS.  The wepons were installed into their MSM or amphibious mobile suits since water based wepons would not function on land.  Later versions of the Mega partice Cannon we installed into Mobile Armors (MA).  These were usually very large, fast, and powerful non-humanoid robots.  Unfortunately for the Pericipality of Zeon too many Mobile Armor prototypes were produced and the full capabilities of each was never uncovered.  A later development of the One Year war was the MAX, AMX, and MSN, a MAX was a large ship like mobile armor usually equiped with beam wepons, whereas a AMX was a semi-humanoid mobile suit with the mobility of a MS and the wepons of a Mobile Armor.  Like the AMX there is the MSN, a mostly humanoid robot with the mobility of a MS and more wepons then a MA. MSN's were much larger than the average MS and came with more fighting capibility then most fleets, one of the most famous MSN's was Char's MSN-02 Zeong, a massive MS-like robot only with no legs, 1 mega-partice cannon in each finger and a head that could run seperately from the body, this was the first MS with a head-cockpit.