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?
Union of Krewo: In a strict sense, the Union of Krewo or Act of Krėva (also Union of Krevo, Act of Kreva) was a set of prenuptial promises made in the Kreva Castle on 14 August 1385 by Jogaila, Grand Duke of Lithuania, in exchange for marriage to the underage reigning Queen Jadwiga of Poland.
i don't know