Was playing Russia, and the Golden Horde/Astrakhan alliance attacked Kazan. I then declared War against Kazan (though I was not part of the GH/A alliance) too and sieged their westernmost city after it had been unsuccessfully sieged by the alliance. I captured this province and then moved east to attack the next Kazan province. The alliance declared a White Peace with Kazan and the province that Russia had captured reverted back to Kazan! Doesn't seem right.