Excerpts from Books and Wikipedia
"The Hungarian advance led to a string of Turkish losses; . . . Murad II chose to accept a ten-year truce with Wladyslaw and John Huniades. This sudden capitulation was only partly related to the Hungarian victories. His oldest and best-loved son Aleddin had just died of a swift and unexpected illness; Murad II was grieving and weary. He was only forty, but he had been sultan for twenty-three years, all of those spent at war. Right after signing the truce, he summoned his next son, twelve-year old Mehmet, to join him at Edirne. There he announced that he intended to abdicate the sultanate and hand it over to the child and his hand-selected vizier, Halil Pasha. This appeared to be a sign of weakness. Suddenly, it seemed that the long-discussed Crusade might actually happen. A papal legate was dispatched to assure both Wladyslaw and John Huniades that they were not bound by the terms of the truce they had just signed, since Murad was an infidel. . . . [Murad II] approached Varna himself at the head of a hundred thousand men, outnumbering the Hungarians three to one. . . . When he joined the battle on November 10, 1444, he carried a standard with the ripped pieces of the peace treaty nailed to its top." [Bauer: Renaissance World, p. 676-7] "Final battle of the Crusade of Varna; Ottomans are victorious over the Hungarian-Polish armies, and Wladyslaw III of Poland dies." [Wikipedia: Timeline of Middle Ages]