Polo, Marco the order were defeated, but the war marked the onset of almost a constant state of tension and intermittent fighting between the Teutonic Order, the Ordenstaat, and the Polish monarchy Casimir III of Poland began to rebuild his country’s military position in the 1340s for what began to look like an ultimate reckoning with the Teutonic Knights In 1385 Jogaila (Jagiello), the grand duke of Lithuania, married Queen Jadwiga of Poland, converting to Christianity He ruled Poland as Ladislas (Władysław) II In 1226 Lithuania had become united when the Lithuanians under their leader, Mindaugas, had defeated the Livonian Knights of the Sword (allies of the Teutonic Knights), at Siaulai This marriage, the result of the Union of Krewo, established the Jagiello dynasty and became the foundation of Polish resistance to the territorial expansion of the order Meanwhile the rule of the order had grown more oppressive, through both taxation and demands on military service, to persecute the war against the Poles and their Lithuanian allies Both Prussians and Pomeranians looked to their former enemies, the now united Poles and Lithuanians, for relief against the Ordenstaat In 1407 his brother Ulrich, who showed contempt for the abilities of the Poles and Lithuanians to confront the Ordenstaat, succeeded Grand Master Konrad von Jungingen In 1410 the order’s grand master Ulrich von Jungingen decided to force the issue before Wladislaus II and a Polish-Lithuanian force could reach the order’s headquarters at Marienberg in Prussia On July 15 the Teutonic Knights met the combined Polish and Lithuanian forces at Tannenberg, or Grunwald Wladislaus’s cousin, the grand duke Vytautas of Lithuania, commanded the actual Polish field army In the fierce combat that followed, as Koch writes in Medieval Warfare, “the Poles concentrated their attack at one point of the German front, broke through and then with their numerical superiority of 3:1 engulfed the army of the Teutonic Order and defeated it.” Although Tannenberg was the decisive battle of the war, the knights did not surrender or cede their territory, and the struggle was continued by Ulrich’s successor Heinrich von Plauen, the 24th grand master of the Teutonic Order For over 50 years hostilities continued between Poland and the order At the same time among the Prussians and Pomeranians, resentment continued against the exactions of the Ordenstaat Finally the situation became untenable for the Teutonic Knights In 1454 the Prussians directly approached King Casimir IV of Poland for aid in throwing off the order’s rule In what became known as the Thirteen Years’ War, the Prussian Confederation fought with Casimir IV 331 against the Teutonic Order Lithuania, the ally of Tannenberg, was also at war with Poland but did not side with the order In one of the first battles of the war at Chojnice in April 1454, Casimir IV was defeated in his attempt to take the city by the order and mercenaries under Bernard Szumborski in its pay Eventually, however, the prolonged struggle outstripped the ability of the order to continue the fight Pope Paul II, with both warring parties being Roman Catholics, stepped in to help negotiate a settlement By the terms of the Treaty of Thorun in 1466, the order ceded control of Prussia Prussia became a vassal state of the Polish Crown under King Casimir IV, who now ruled a unified Poland, which would emerge as the strongest state in eastern Europe Further reading: Bernstein, Carl, and Marco Politi His Holiness: John Paul II and the History of Our Time New York: Penguin Books, 1996; Eggenberger, David An Encylopedia of Battles Mineola, NY: Dover, 1985; Grousset, René The Empires Of The Steppes: A History of Central Asia Trans by Naomi Walford, New Brunswick, NJ: Rutgers University Press, 1970 John F Murphy, Jr Polo, Marco (1254–c 1323) explorer and author Marco Polo, a Venetian merchant, lived for many years in Mongol-ruled China and wrote about what he witnessed there He is the best known of the many medieval European traders and priests who traveled in Asia beyond its Mediterranean and Black Sea ports When he was a child, his father and an uncle visited China They returned with a letter from the emperor to the pope When the two Polo brothers made a second journey to China, they took Marco with them, then in his teens He spent nearly two decades, from the early 1270s to the early 1290s, in China, where he became a favorite of Kubilai Khan, of the Mongol Yuan dynasty (1279–1368) After Marco Polo returned to Italy, he introduced Europe to the wonders of Cathay, his name for China Using notes as well as memory, he described what he had learned in a book written in collaboration with an experienced writer, Rustichello of Pisa, while both men were prisoners of war in Genoa Writing in a French-Italian dialect, Rustichello adapted Polo’s story to the fashionable genre of chivalric romance Immediately popular, the book was translated into Latin and several vernacular languages during Polo’s lifetime