Question: What queen's marriage was a condition of the promises in the Poland-Lithuanian union that was threatened to be severed by the Lithuanian Civil War?
Sentence (from "Lithuanian Civil War (1432–38)"): The war was fought on the one side by Švitrigaila, allied with the Teutonic Knights, and on the other by Sigismund Kęstutaitis, backed by the Kingdom of Poland.
Relevant evidence: No