The Battle of Nicopolis in 1396 was part of a European Crusade, and incredibly demoralizing for Europe, because the Ottomans defeated an army of Hungarian, Croatian, Bulgarian, Wallachian, Polish, French, Burgundian, German, English, Knights Hospitaller, Iberian, Italian, Bohemian, Serbian, and Byzantine troops. Sigismund was at their head, so it was particularly bad for him. The defeat and loss of several men angered Hungarian lords and led to instability in Hungary. It was at this point that Sigismund met with Jadwiga and Jogaila and offered to mediate between them (Poland and Lithuania) and the Teutonic Order, starting the process that would lead to cessation of the Teutonic Crusade against Lithuania.
Although Jadwiga and Jogaila had seemed to be a good match, working together now for over a decade, they had not yet produced an heir. Contemporary chroniclers claim this was a source of friction for her husband. She finally became pregnant in late 1398. The current Grand Duke of Lithuania, Jogaila's cousin Vytautas, sent a silver cradle for the child, who was predicted by astrologers to be a son. On 22 June, 1399, a daughter was born and given the name Elizabeth Bonifacia. Elizabeth was the name of Jadwiga's mother, and the second name was for Pope Boniface IX, who agreed to be godfather.
Sadly, Elizabeth Bonifacia died a few weeks later, followed four days afterward by Jadwiga. Mother and daughter were buried at Wawel Cathedral on 24 August, 1399.
What followed for Jogaila? Jadwiga had a hand in that. On her deathbed, she advised him to marry again, this time a granddaughter of Casimir III "the Great." And so Jogaila took a second wife on the advice of his first, the teenaged Anna of Cilli. I'll tell you her story tomorrow