After the end of the Gryps War, the Earth Federation was extremely weakened not only due to the loss of the Titans. The AEUG also lost a majority of its forces and, apparently, only the Argama was still able to fight. Only the Axis fleet was still intact because it retreated from the battle to prepare for their invasion of Earth. Four months after the last battle of the Gryps War on February 29, U.C. 0088, "Axis Zeon" renamed itself Neo Zeon and started the First Neo Zeon War.
The First Neo Zeon War
Since the Earth Federation and the AEUG were greatly weakened, the Neo Zeon fleet sent an invasion force with the goal of seizing control on Earth. With the help of some remaining Principality of Zeon members on Earth, the Neo Zeon troops were able to secure several locations in Africa with nearly no resistance because of the damage the Federation forces took in Africa during the Gryps Conflict. Haman Karn also tried sending troops to each colony in space, but failed because of high concentrations of Federation forces in the colonies who were relatively undamaged by the Titans and AEUG civil war. However, remnants of the AEUG would mount a resistance to Haman's Neo Zeon forces in Africa, via the remaining crew of the Argama, alongside new AEUG recruit and pilot Judau Ashta, who was selected as the new pilot of the Zeta Gundam.
On August 8 U.C. 0088, Haman's forces conquered the Earth Federation Assembly at Dakar, but when the AEUG and Karaba attacked, they were forced to retreat.
On October 31 U.C. 0088, the Neo Zeon army dropped a colony on Dublin, Ireland as part of their show of intimidation. Prior to the drop Neo Zeon sent their forces to cut off all means of escape for the civilians to further their cause for this operation and thwarted any attempt for the civilians to flee. While this operation killed most of the residents, the interference of the AEUG and Karaba enabled some of the civilians to be rescued safely and transported out of Dublin aboard Karaba's giant aircraft the Audhumla, though Karaba's leader Hayato Kobayashi died during the battle. Not wanting any further colony drops, the Earth Federation Government agreed to give the Side 3 colony, Core Three, over to the Neo Zeon.
Neo Zeon Civil War
On December 25, U.C. 0088, Glemy Toto declared the foundation of his own Neo Zeon faction, which sparked a civil war against Haman's main forces. Haman had been establishing her new base of operations at the Side 3 Core Three, and while she was gone, Glemy staged an uprising at the main Neo Zeon base of Axis and took control of it. Then he proceeded to attack Core Three to eliminate Haman once and for all. The AEUG and Haman's loyalists decided that Glemy was the greater threat, and engaged with his forces inside Axis, eventually eliminating Glemy. As a last ditch effort, Glemy had ordered his troops to ram both Axis and its satellite asteroid Moussa into Core Three, destroying both Haman's and Glemy's remaining fleets. Haman herself would be killed in battle with Judau and his ZZ Gundam. This three-way struggle between the AEUG, Haman's Neo Zeon, and Glemy's separatist faction takes place at what's known as The Battle of Axis. The first Neo Zeon War finally ended on January 17, U.C. 0089.
With the deaths of Glemy Toto and Haman Karn, Neo Zeon was leaderless. Also, a great part of its fleet was wiped out during the civil war. However, Char Aznable would return later, in U.C. 0090 and took control of the remaining Neo Zeon forces, which led to the second Neo Zeon movement.
Second Neo Zeon Movement/Char's Rebellion
To deal with anti-Federation movements, the Earth Federation created the Londo Bell Task Force, whose mission was similar to the Titans, albeit without its fascist overtone. Due mostly to the fact that members of the Londo Bell are former members of the AEUG, operations are carried out in a far more humane way; however, Londo Bell was greatly understaffed.
In the end of U.C. 0090, the presumed dead Char Aznable returned and became the leader of Neo Zeon. As the son of Zeon Zum Deikun, Char took it upon himself to move all humans into space, so that the Earth might become a natural sanctuary; however, the means by which he attempts this end are far more radical, as he forces Earthlings to flee into space by dropping asteroids onto Earth, thus starting a nuclear winter. Char's forces are successful in gaining favor from the colony of Sweetwater from which, on 27 February U.C. 0093, they declare war against the Earth. In order to stop Char, the Earth Federation increases the Londo Bell's size and prominent veterans from the former wars, such as Bright Noa and Aznable’s old archrival Amuro Ray, are added. Thus, the Second Neo Zeon War began.
The Second Neo Zeon War
The first major battle of the Second Neo Zeon War takes place when Char tries to drop the asteroid Fifth Luna on the Federation’s headquarters in Lhasa, Tibet. Although Londo Bell interferes, they fail to stop the operation and Lhasa is completely destroyed. Afterward, Char retreats to Sweetwater, while Amuro uses his incomplete RX-93 ν Gundam to repel a Neo Zeon attack against the Londo Bell flagship, Ra Cailum.
On March 6 U.C. 0093, the Earth Federation holds a secret meeting with Neo Zeon representatives, including Char, at the colony Londenion of Side 1. Char agrees to stop the attacks and surrender his fleet, if the Federation hands him Axis. Representatives of the Federation agrees to his terms. Later, Char and Amuro have a short encounter on the landscape of the colony, where 13 year-old Quess Paraya, the daughter of one of the Federation representatives, allies herself with Char and helps him escape.
A few days later, Char sends a dummy fleet to the asteroid, Luna II, while his main fleet capture Axis by force. They are successful, but Londo Bell launches nuclear missiles against the asteroid. However, all are single-handedly destroyed by Cyber-Newtype, Gyunei Guss. Afterwards, Londo Bell plans to place explosives inside Axis to break it apart, thus deflecting it from Earth.
When the operation starts, Amuro and Char, who pilots the MSN-04 Sazabi, engage one another at Axis. Londo Bell is successful with planting the explosives inside Axis, but only a part of the asteroid is deflected. Amuro, who in the meantime has defeated the Sazabi and taken Char's evacuation pod with him, tries to stop the falling asteroid with his ν Gundam. Later, the Federation mobile suits and even Neo Zeon troops attempt to push Axis out of Earth's atmosphere. Axis is finally pushed away from Earth when a strange reaction inside the psycommu system by the psycoframe of the ν Gundam creates enough power to stop the asteroid and push it out of Earth's gravity. The Second Neo Zeon War comes to an end.
With the supposed deaths of Amuro Ray and Char Aznable, the last great leader of Zeon, the Second Neo Zeon War ends with the Earth Federation victory. However by U.C. 0096, the Neo Zeon would regroup and reorganize under a new leadership of a man named "Full Frontal" and renamed themselves as "The Sleeves" thus restarting the conflict one last time.
Three years after the Second Neo Zeon War, the remnants of Neo Zeon also known as "The Sleeves" under the command of Full Frontal, who is known as "the Second Coming of Char" and the Vist Foundation are about to trade a secret about the Universal Century, which is the Laplace's Box, but they do not know that the Earth Federation knows about this. This will be the start of the Third Neo Zeon War/Laplace Conflict.
The Third Neo Zeon War/Laplace Conflict
After the Laplace box was open and the Full Frontal reuntied with his other half Char, "The Sleeves" was eventually disbanded, thus the long conflict between the Earth Federation and the remnants of the Principality of Zeon finally ends. In U.C. 0100, Zeon gives up its autonomy and rejoins the Federation, who declares the eradication of all conflict in the Earth Sphere and its surrounding colonies.