During the years of 2275-2276, a force known of Caesar's Legion began to push on Brotherhood holdings in Colorado. The Midwest Brotherhood, recognizing the Legion as a serious threat to the security of the region and their mission there, sent a few squads to push back what they though was a small band of ludicriously dressed raiders who had learned Latin. The Brotherhood was terribly wrong.
After learning the true nature of their adversary, the Brotherhood began a full scale campaign againt the Legion. While the Brotherhood had superior weapons and tactics, they were simply outnumbered by the forces of the Legion. The Brotherhood was forces to relinquish their holdings in Colorado and western Kansas.
Defeat seemed imminent for the Brotherhood, but suddenly in 2277, the Legion suddenly stopped its advance, redistrubuting their troops to some unknown battlefield. The Brotherhood, their ranks and supplies severely diminished, returned to their holdings in Missouri and Illinois, only to find that many of the villages they had brought into their fold now rejected Brotherhood rule. Forgotten during the fight with the Legion, the local settlements had been attacked by raider and other forces, and as the Brotherhood had failed to live up to their part of the deal in proctecting them they no longer wished to provide the Brotherhood with manpower and supplies, and the Brotherhood did not have the forces to reclaim their holdings. Broken, the Brotherhood was forced to start from scratch again, in the hopes that the Legion would need just as much time to regroup and mount another attack on the region.