The Battle of Grunwald, sometimes referred to as the Battle of Tannenberg, was a decisive clash in the Polish-Teutonic War of 1410, a conflict in which the monastic state of the Teutonic Order was crushed by the Poles and the Lithuanians. Most of the leadership of the Order was killed in combat, and the Polish-Lithuanian alliance emerged as the dominant force in eastern Europe.

- Polish-Teutonic War and Lead-Up to the Battle -

The Teutonic Order was originally formed in the Middle East, during the Crusades, but after the fall of the Crusader states there it moved north into eastern Europe during the 1200s and carved out an independent state, justified in the name of converting the pagan inhabitants of Prussia and the current-day Baltic states to Christianity.

The knights’ fledgling state grew quickly and ultimately attained considerable power during the 1300s. However, a combination of political and economic stagnation and cripplingly high tax rates made its condition surprisingly precarious. In 1409, Lithuania backed an internal rebellion and subsequently obtained Polish assistance, as well. The Teutonic Order invaded Poland, hoping to quickly eliminate the Poles and then turn and deal with the suddenly isolated Lithuanians. The result was an unsuccessful attempt to capture (which was done) and hold (which was not) Dobrin and Bydgoszcz.

At this point, outside forces stepped in to mediate; the King of the Romans (at the time the title for present-day Germany), Wenceslaus, attempted to arbitrate by ruling that the territory in which the rebellion had started, Samogitia, was Teutonic and therefore that the Poles and Lithuanians had no claim to it or right to intervene there. The ruling was the result of a handsomely large bribe from the knights, however, and before the year was out the kings of the Poles and Lithuanians decided to unite their armies under a single banner and besiege the Teutonic capital, Marienburg. They brought between 16,000 and 40,000 (estimates vary wildly) troops with them as they marched into Teutonic territory. Precisely how large the force the Order could muster to impose this invasion is also uncertain, although chroniclers agreed that it was both substantially smaller, but also much better trained and better armed.

- Battle of Grunwald -

In June 1410, Polish, Lithuanian, Masovian, and Ruthenian soldiers, along with Czech mercenaries under Polish authority, met along the Vistula River and crossed into the Teutonic state. The crossing was intended to be conducted in secret, and seems to have been successful in doing so - until, that is, Hungarians still attempting to mediate between the two sides mentioned the crossing to the head of the order, Teutonic Grand Master Ulrich von Jungingen. Jungingen hastily assembled a force of his own and, in July, fortified a crossing at the Drewenz River where the Polish-Lithuanian army was expected to cross. As a punitive strike, the invading army, either as a provocation to enrage Jungingen or simply as an opportunity for some always-hoped-for looting (one of the main functions of medieval combat was always to enrich the participants), sacked a civilian town, Gilgenburg.

On July 15, Jungingen was able to force confrontation between Grunwald and Tannenberg (both villages). Confident of victory, Jungingen arrayed his men in battle formation (with the most skilled heavy cavalry in front of the Lithuanian section of the line), waited for the Poles and Lithuanians to assemble themselves for combat, and even, as a final insult, sent a pair of swords to the Polish and Lithuanian kings, warning they would need them to defend themselves in the coming rout. The Grunwald Swords are now Polish symbols. Ominously for the Order, Jungingen attempted to fire his cannons to win first blood; in the rain, few shots were successful.

Vytautus, the Lithuanian king, now moved first, charging the Teutonic left flank and then, after some unsuccessful skirmishing, retreating with heavy losses. The retreat seems to have been a whole-hearted and disorganized one; some historians suggest that given the totality of the Lithuanian flight, it may even have been a feint designed to draw the Order’s forces out of position. False retreats were tactics which had worked before, and which Europeans had learned from the Mongols. In any case, as the retreat began, the Order also advanced against the forces surrounding the Polish king, Jogaila.

The battle was a close-fought one, and while the decision hung in the balance, the outcome was decided by the surprise return of the Lithuanian cavalry to the battlefield, charging directly in from behind Jungingen’s engaged forces. (It is this attack from behind which has led some historians to believe the initial retreat was a false one. Crushed between the Polish and Lithuanian forces, the Order’s army was defeated in detail. Jungingen was killed, as were many of his fellow senior members of the Order. Later, those who survived claimed that one Nikolaus von Renys, a knight commander believed sympathetic to the Polish cause, had deliberately sabotaged the battle effort by lowering his banner, prompting mass confusion in which some units surrendered to the Poles, and others fled the field entirely. Whether Renys was actually to blame is dubious, though he was promptly executed for his alleged crime.

- Results -

Altogether, about 16,000-39,000 Poles, Lithuanians and allies had faced off against about 11,000-27,000 Teutonic soldiers and won decisively. Losses were heavy on both sides: about 5000 killed among the Poles and Lithuanians, and 8000 on the Teutonic side, including two hundred knights. However, twice that number of Teutonic troops surrendered, and less than 1500 of those who fled actually made it back to the capital of Marienburg. As was the custom, prisoners of noble birth were exchanged for sizeable ransoms; commoners who could command no ransom were typically released, unless some reason was found to abuse them further.

Fresh from victory, Vytautus and Jogaila led their forces onward to besiege Marienburg after several days’ rest. This time they were unsuccessful as, although the Order was in tatters, they received prompt Hungarian, German, and Livonian military assistance. This only bought them a brief additional time, though. In the fall, the Order’s fledgling forces were defeated again at Koronowo. Over the winter, they signed the Peace of Thorn, ceding disputed land to both Poland and Lithuania and imposing war reparations. When they raised taxes to cover the reparations, the Knights found themselves beset by internal rebellion. Eventually, in the 1450s, the Poles would aid an upstart Prussian Confederation in throwing off Teutonic rule. That final war ended the independence of the Teutonic state.