Jovian Wars
The Jovian Wars, also sometimes called the Hyperion Wars, are a grouping of possibly ongoing territorial and Paradigmatic battles taking place on the Jovian and Saturnine moons in Mage: The Ascension. It is considered a subset of the larger Ascension War.
The ETD recognizes the formal beginning of the conflict as 1944, and places the ending in 2001. That said, isolated enclaves continued hostilities until quite recently. And obviously, joint offenses against the Nephandi and Marauders are still ongoing.
History
It is not recorded precisely when the first outpost of the Celestial Masters was built around the gas giants, but the Order of Reason has displayed an interesting in colonizing the outer moons at least since the catastrophic failure of an attempt at an experimental gas harvesting complex on the "surface" of Jupiter.
At the same time, the earliest descriptions of space within the Near Horizon already had it overrun with Marauder and Nephandi, causing the Jovian and Saturnine colonies to be heavily militarized.
By the late 1800's, the Technocracy had largely consolidated control over the two giants orbits. This would prove short lived, however, as the Etherites would ultimately pull Ganymede with them when defecting to the Traditions.
The groups existed in an uneasy detente until World War II, when they were forced to unite in attempt to finally expell the Nephandi from the Near Universe, establishing a Sentinel Satellite network around Io to monitor Nephandic activity.
Unfortunately, the alliance would prove short-lived, as the newly formed, PTSD-riddled Jovian Veterans Unit became among the most zealous Pogrom supporters of the postwar Union. They redoubled efforts to expell Reality Deviants from the gas giants once and for all, beginning a decades long war that would stretch the resources of both the Jovian and Saturnine colonies and the Copernicus Research Center itself.
Conclusion
Early sources indicated that, while Jovian colonists on all sides had access to enough natural Quintessence to avoid the Void Adaptation that afflicted the inhabitants of fully constructed Horizon Realms, the Avatar Storm cut off communication with both contacts on Earth and DSEATC on the Cop, leaving the Jovians to continue their struggle in isolation indefinitely.
More recently, however, the Pan Dimensional Corp seems to have regained some degree of contact with their counterparts on Europa, and have issued orders to cease excessive hostilities towards the Traditions and non-hostile aliens, citing the approach of a much more severe threat that may require assistance from outside the Union to defeat.