After the War of Dissolution, the Partisans were still on the war path. The old Claravian hierarchy was laid low, but the Partisans wanted to make sure it could never rise again, and the only way to do that, at least if you asked the Partisans, was with the Partisans in charge of the whole system. The old secular governments of the inner planets weren't about to let themselves be subjugated again just after throwing off the hierarchy's yolk, and many policymakers felt the only way to keep the space tree doggo Commies Partisans at bay was to present a united front. So while some weren't too pleased with chaining themselves to Yih again, the inner planets save Hearthside formed an economic and military federation to counter the Partisan threat.

While most of the governments involved tolerated the now economically gelded Bright Way, they still wanted to keep them at tail's length, so the ecclesiocratic Hearthside was explicitly kept out of the alliance. This despite Hearthside being the stronghold for the Pious Dissolutionists, who were instrumental in turning the tide of the war.

It worked out well for Hearthside in the end, since they still had a hefty buffer between them and the Partisans. The subsequent cultural homogenization that among other things saw Commonthroat become the de facto standard language didn't affect them as much as it did the AW, and Hearthsider remains a living, albeit declining, language at the time of First Contact.