The Preventers organization was formed by the Earth Sphere Unified Nation, to prevent conflicts from escalating. The Preventers use code names such as "Water" (used by Sally Po), "Fire" (used by Lucrezia Noin), and "Wind" (used by Zechs Merquise).
- Sally Po - Water
- Lucrezia Noin - Fire
- Lady Une - Gold (Endless Waltz novelization only)
- Zechs Merquise - Wind
- Chang Wufei
- Kathy Po
Barton Foundation Investigation
On the colonies, there were the movements of the Barton Foundation, the original architects of Operation Meteor. This didn't go unnoticed by the Preventers or the Gundam Pilots. Heero and Duo planned on infiltrating Colony L3 X-18999 to rescue kidnapped Vice Minister Relena Darlian. Sally and Lucrezia assisted them by destroying the mobile suits guarding the entrances.
Mariemaia Earth Invasion
The Mariemaia Army was poised to invade Earth, due to the dissolution of its armed forces. However, as the first wave of transports deployed, the Tallgeese, piloted by Zechs Marquise, destroyed all of them. Unfortunately, as he was poised to destroy the MA base, Dekim Barton threatened to drop colony L3 X-18999 onto Earth, thus completing the original Operation Meteor. Zechs had no choice but to let the other transports go past.
Luckily, the Gundam Pilots disabled X-18999 and prevented it from dropping, allowing Zechs to destroy Dekim's base. However, Dekim managed to escape.
The ESUN capital of Belgium was invaded by the Mariemaia Army, taking control of the Earth Sphere. The only opposition was three Gundams, the Tallgeese, and one Taurus, all of which fought until they ran out of energy. They were able to significantly disable the majority of the MA. It wasn't until the populace decided to stand up against the Bartons and Dekim was killed by one of his own men that true peace reigned over the Earth.
In the year Mars Century (M.C.) 0022, Preventer agent Kathy Po, daughter of missing agent Sally Po, is given orders by ESUN President Dorothy Catalonia to launch a mission known as Operation Mythos. She meets her superior officer Master Chang at the Mars Preventer Base to deliver vital data and information of the orders received. There, she meets the awakened pilot Heero Yuy, who joins the Preventers along with a mysterious priest named Father Maxwell and his son Duo for the mission.
- OZ-00MS2B Tallgeese III
- Snow White
- Preventer Cruiser
- Preventer Shuttle