Combatants: Yuke and Joseo-Velkan coalition
The shortest but most destructive cluster-spanning war of the Tangeal Expanse bar the Reaper War. While still firmly in the rebuilding and scavenging phase, the leaders of Joseo and Velka had reached an understanding that the Genophage cure should never reach the cluster, or it would force a war with the Federation of Yuke unconstrained by the sterility plague.
After opening of the Future Corridor, in the face of strict security measures, smugglers managed to bring soil samples from Tuchanka with the cure carried in them. Realizing that the growth had to be stopped now, or future generations would be subjected to an unstoppable horde of krogan aggressors, the Joseo-Velkan coalition declared war on Yuke with intent to end the threat permanently.
Remnants of each nations' navies engaged and disarmed the Yuke navy in its entirety. Coalition forces then resorted to genocide through WMDs to cull the krogan numbers, until no organized resistance remained on the Yuke worlds. Those worlds with the capability to still support sapient life were incorporated into the remaining two states, including independents that no longer had the benefit of being useful as neutral buffer states.