Mobile Suit Gundam introduced some of the most iconic mecha in all of anime history. However, while the original series started with mech suits being a standard weapon in warfare, they had an origin. How did the first suits -- the precursors to the Zaku and Gundams -- develop during this massive war? What was the point of these walking tanks?
When diving into the deeper lore of Gundam, one inevitably comes back to Mobile Suit Gundam: The Origin, a prequel series that outlines the gradual grind that led to The One Year War, where Amuro Ray in the RX-78-2 Gundam fought back against the Principality of Zeon. Mobile Suit Gundam: The Origin lays the groundwork for the mecha suit arms race, demonstrating the gradual evolution into the Gundams and Zaku suits.
The AMBAC Technology and the Rise of the Zaku
During the Universal Century era, the conflicts between the Principality of Zeon and the Earth Federation was waged with more traditional weapons at first. The Earth Federation's primary weapon was the Type 61 Tank -- which was, as the name implies, a powerful tank with a large cannon on top of it. To compete with these weapons, Zeon developed ones even more powerful to combat them.
The AMBAC system -- or Active Mass Balance Auto Control system -- is one of the key technological advances necessary to create giant mobile suits that could walk and balance themselves on two legs. It was revealed in the art book Mobile Suit Illustrated 2003, along with another significant piece of technology, and divulged the Principality of Zeon's first tests of the AMBAC system.
Two companies commissioned by Zeon, the MIP Company and Zeonic Company, produced two spacecraft with developmental arms and weapons: the MIP-X1 and AMBAC Space Pod. Zeonic's AMBAC Space Pod proved the more successful suit, leading to Zeon giving them a military contract to develop their Mobile Suits further. However, the MIP-X1 would eventually be redeveloped into the MA-05 -- a crab-like spacecraft seen in the Mobile Suit Gundam series directly.
This, combined with the Minovsky Particle development -- a subatomic particle produced by portable nuclear power generators that blocked out radar and other long-range radiation -- created an environment where wars had to be fought in close-ranged combat. It was through this that Zeon and Zeonic developed the first mobile suits: the MS-01 Zaku. This would be upgraded over time, eventually becoming the iconic MS-05 Zaku and its multiple variants we saw in the One Year War, shown in Mobile Suit Gundam.
Earth Federation's Operation V
Upon encountering Zeon's early Zaku models, Earth Federation initiated Operation V -- also known as Project V or Project Victory -- a process in which the Earth Federation developed their own mobile suits. Operation V served as the start of a massive arms race that would culminate in creating the RX-78-2 Gundam.
The Earth Federation transitioned development on their upgrade to the Type 61 Tank -- the RTX-44 -- into the RTX-440 Ground Assault Type Guntank (seen in the CGI OVA Mobile Suit Gundam MS IGLOO 2: The Gravity Front) and the more well-known RX-75-4 Guntank. The RX-75-4 Guntank was a tank-like long-range weapon capable of devastating all the mobile suits who came in their way.
However, Earth Federation's first genuine mobile suit was the RX-77 Guncannon, a powerful mech with two mounted cannons atop its shoulder. However, they were expensive to make and only developed in small quantities. It also valued mid to long-range combat over close-range combat, something that proved to be a massive failure when Zeon's close-range fighters, the Zakus, emerged on the scene.
This immediate need for close-range fighters led Amuro Ray's father, Tem Ray, to convince his superiors to develop a short-ranged mobile suit capable of annihilating all in its path -- ultimately leading to the creation of the iconic RX-78-2 Gundam.