In the early 2160s, the Alliance began aggressive colonization of worlds in the Skyllian Verge, much to the dismay of the batarians who had been developing the region for several decades. In 2171, the batarians petitioned the Council to declare the Verge a "zone of batarian interest". The Council refused, however, declaring unsettled worlds in the region open to human colonization.

In protest, the batarians closed their Citadel embassy and severed official diplomatic relations with the Council, effectively becoming a rogue state. They instigated a proxy war in the Verge by funneling money and weapons to criminal organizations, urging them to strike at human colonies.