Combine-Covenant War

The Combine-Covenant War is an ongoing conflict between the Combine (Universal Union) and the Covenant, over a Halo Ring in the Milky Way. The Halo was first discovered by the Cironeans, who swiftly colonized it. Later, the Covenant discovered the ring, and took it from the Cironeans. Shortly after the Covenant began landing troops on the ring, the Union tunneled in a (relatively) small scouting fleet, to stop the firing of the ring. The Covenant refused to hand over the ring, thus sparking the conflict.

While the battle was being fought, an Advisor communicated with the Covenant shipmaster, and turned it over to the Combine side. A civil war broke out within the Covenant, and the war has been ongoing since.