The battle was one of the longest and bloodiest of the Middle Ages. The Grand Master Ulrich von Jungingen and all the order’s officers but one lay dead on the field, and the whole of Prussia was there for the taking. Much to the exasperation of the Polish commanders, Władysław reined in the pursuit and in the treaty signed later he demanded only a thin strip of land to be ceded to Lithuania, and nothing for Poland, while taking a vast cash indemnity from the order for himself. A decade later the knights made war again, were again defeated, and again got away with insignificant losses. In 1454 a revolt against the order by local knights and cities, aided by Poland, initiated a war which dragged on for thirteen years. The knights were defeated, and were once again spared, by the Treaty of Toruń in 1466. Poland took the coastline around Gdańsk and Elbing, the province of Warmia (Ermland), and even the stronghold of Marienburg, but did not suppress the order, which moved its capital to Königsberg and retained the rest of its dominions as a vassal of the king of Poland. Such forbearance might seem surprising, particularly as the Teutonic Knights were ruthless in war, raping and murdering, and even burning churches. There were, however, factors involved in the relations between Poland and the order that touched on a religious debate of European proportions.
The Teutonic Order had representatives and friends at every court, and was a master of propaganda. Its first line of attack had been that the betrothal of Jadwiga to Wilhelm of Habsburg had been consummated and that her marriage to Władysław Jagiełło was therefore bigamous. It also argued, with some justification, that the alleged conversion of Lithuania was a sham, and that Catholic Polish knights had been the minority at Grunwald in an army made of Lithuanian pagans, Christians of the Eastern rite, and even Muslims (the Tatars who had settled in Lithuania some time before). The order suggested that Władysław Jagiełło’s army was hardly more Christian than Saladin’s.
The Teutonic Knights had a point, and that point assumed importance in the context of a minor reformation which was sweeping Europe, a nationalist, anti-clerical, anti-Imperial movement whose greatest exponent was the Bohemian Jan Hus. The Hussite movement was itself connected with John Wycliffe’s Lollards in England, and both causes enjoyed considerable sympathy in Poland.
Matters came to a head at the Council of Constance, convoked in 1415 to combat the Hussite heresy. The Teutonic Order saw in this a perfect forum at which to discredit Poland and reconfirm the validity of its own crusading mission, judging that if this were endorsed by Christian Europe, it would have placed itself beyond the reach of Polish attempts to destroy it.
The Polish delegation to the Council of Constance, led by Paweł Włodkowic (Paulus Vladimiri) of Kraków University, included a number of Lithuanians and schismatics, which caused uproar and favoured the order’s case. Włodkowic ran rings around its representatives and managed to discredit it. But there was no clear-cut victory. The Teutonic Knights enjoyed wide diplomatic support, including that of the Empire, which had political objections to the Polish-Lithuanian union.
The arrangement itself was under frequent review. In 1413, after Grunwald, a new treaty of union was signed at Horodło. This attempted to bind the two states together more firmly, and was epitomised by the Polish szlachta adopting the Lithuanians as brothers in chivalry, bestowing on them their own coats of arms. In 1430, Vytautas’ successor as Grand Duke of Lithuania, Svidrigaila, undid all this by allying himself with the Teutonic Order and adopting an anti-Polish policy. Ten years later, the union was formally dissolved, but this made little difference, since the ruler of Lithuania was the son of the King of Poland, whom he succeeded in 1446, reuniting the two states under one crown.
The unstable nature of the union was largely the result of incompatibility. Poland was a nationally based Christian state with
developed institutions and strong constitutional instincts. Lithuania was an amalgam of pagan Balts and Orthodox Christian Slavs ruled by an autocratic dynasty. The two states pulled each other in different directions, and in the field of foreign policy it was Lithuania, or rather the Jagiellon dynasty, which pulled the hardest.
It is no coincidence that the oldest extant letter from a king of England to a king of Poland dates from 1415, when Henry V begged Władysław Jagiełło to assist him against the French: the union with Lithuania and the victory over the Teutonic Order had turned Poland into a major European power. And it is hardly surprising that with such power behind them, the ambitious Jagiellons should have taken advantage of the opportunities on offer.