By Dmetrius Dviochenko de Markov
From Crecy to Mohacs: Warfare in the Late Middle Ages (1346-1526): 22nd Colloquium of the International Commission of Military History (Vienna, 1997)
Introduction: In 1386, following the dynastic agreement of Krewo of 1385, the Grand Prince of Lithuania, Olgerd (Olgirdas), was succeeded by his son Jagiello (Jogaela, 1377-1434). He married Queen Jadwiga of Poland, the daughter of Louis the Great, and converted from Christian Orthodox faith to Roman Catholicism thus becoming the legitimage sovereign of both states of Lithuania and Poland under the name of King Wladislaw II.
In 1392 Jagiello had to recognize his cousin, Keistut’s son Vitovt (Vytautus), as a seperate vassal, the Grand Prince of Lithuania (1392-1430). Under Vitovt’s rule we can establish the greatest extension of the Lithuanian state in control of the Russian lands of Volynia, Kiev, Polotsk, Chernigov, and a large part of Smolensk. Vitovt was able to challenge Moscow for supremacy on the great Russian plain. The German Teutonic Order organized several crusades against pagans and Christian Orthodox schismatics in the spirit of “Drang nach Osten” (“Push to the East”) and conquered lands from Lithuania and Poland along the Baltic coast from the Gulf of Finland and beyond the delta of the Elbe river.