When Anubis regained his place among the System Lords, he set about systematically decimating the forces of the remaining Goa'uld. Yu began rallying the other System Lords against him, but even the collective forces of the System Lords failed to stand against Anubis's superweapon. As Yu's mental competence began to fail, SG-1 approached Ba'al with the proposal to turn against Anubis and take Yu's place as the commander of the combined forces of the System Lords. In the battle of Kelowna, Ba'al's forces defeated Anubis's fleet, and Ba'al began to consolidate and expand his power, taking control of what came to be known as the United Alliance of the System Lords, a union for which the SGC was partially responsible.
Cross Reference: Anubis, Ba'al, System Lords, Yu
Episode Reference: Homecoming, Orpheus