Inner Colony Wars
From Halopedia, the Halo wiki
The Inner Colony Wars were a series of conflicts that occurred sometime in human history following the establishment of the Inner Colonies in 2362. Uninformative media coverage of the conflicts sparked widespread civil unrest and nearly destroyed Earth's culture.
The Inner Colony Wars have never been referenced outside the story "Second Sunrise Over New Mombasa" in the Halo Graphic Novel. Assuming the Inner Colony Wars were a distinct event they must have occurred sometime after 2362, as the formation of the Inner Colonies occurred in the mid-to-late 2300s. Since there obviously was no distinction between the Inner and Outer colonies before the establishment of the Outer Colonies, the conflict may have occurred in the 2400s. However, it is possible that the name "Inner Colony Wars" was applied in later years, as the story where the event is referenced takes place in 2552.
The conflicts were most likely not very widespread or involve extensive space combat, as the Insurrection was the first conflict in which the UNSC partook in major space battles, their prior experience with space warfare having been limited to settling minor trade disputes or anti-piracy operations; actual space battles were still entirely hypothetical to UNSC commanders by the 2490s.
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