The Teutonic Order had the will of Western European Christianity behind it, due to the high pagan populations in the area in question and the military might of the order itself. Some 6,000 mercenaries from England, France, Holland, Hungary, Austria, and Germany answered the call to crusade. These took their place alongside roughly 25-28,000 Teutonic Order soldiers, according to Stephen Turnbull. They were commanded by Ulrich von Jungingen, the Grand Master of the Order, Kuno von Liechtenstein, and Frederic von Wallenrode, the Grand Marshal of the Order.
King Jagiello could count upon a sizable force from his ally, Vytautas the Great of Lithuania. From Kiev came some 1-3,000 Tartars commanded by Jelal-el-din, and the Russians under Lengvenis sent additional forces. The Poles also had a small number of field artillery pieces; Varvounis and Ziogaite give the figure sixteen.
Many different estimates exist as to the total sizes of the armies. The Lubeck Chronicle places the Polish/Lithuanian army in the millions, but Turnbull has hedged an estimate of 39,000, including the foreign allies. This battle was, even by the smallest estimates, one of the largest in Medieval European history, particularly in an age when most battles were either small skirmishes or static sieges.
This battle was a showcase of King Jagiello's tactical skill. Despite his commanders' urging to attack, Jagiello did not engage the Order immediately. His enemies were in full armor in the hot July sun, and he must have known that they would become agitated in the heat.
Vytautas the Great was the first to attack, leading his Lithuanian knights, a squadron of Tartars, and some of the Russians. Their attack was focused upon the enemy's right, with the aim of neutralizing their field artillery. The Teutonic artillery managed to fire two volleys, but it did little before it was overrun by the Lithuanians.
The Grand Master, in response, ordered his knights to attack. This played into Jagiello's hand; He wanted to engage the more heavily-armed and better-trained enemy on his own terms. The Tartars, however, fled in the face of the Teutons' charge, and the Lithuanians soon fell back as well. The Teutonic Knights, eager for glory, pursued them to a nearby wood, only to be ambushed by a mass of Polish knights. The Lithuanians rallied, and attacked with some of the Tartars, and their infantry. The battle was going entirely in Jagiello's favor.
At this point the Teutons were surrounded by their enemies. Jagiello himself had led a charge into the swirling melee, and von Jungingen was fighting alongside his knights. The Order had, according to Varvounis and Ziogaite, sixteen regiments as a reserve, which they now brought up for relief. It was, however, too late.
The legend surrounding this battle is that von Jungingen was surrounded by peasants and hacked down. Whether this is truth or nationalistic myth is not known. Either way, the Grand Master fell that evening, and the rest of his army lost heart and fled or surrendered.
The battle was a stunning victory for the Poles and Lithuanians, and an utter defeat for the Teutonic Order. Much of the order's leadership was killed, including all of the main commanders and the majority of the two hundred and fifty brothers of the Order.
The Knights never recovered from this defeat. Demitrius Dvoichenko de Markov states that "The battle... was instrumental in destroying the legend [of] the invincible Teutonic Order." The states of Eastern Europe ceased to rely upon them for security. Worse, the crippling taxes necessary to pay for the reparations demanded by the peace treaty which followed found the Order's kingdom mired by rebellions soon thereafter.
Stephen Turnbull compares this battle to Agincourt, as it has been a source of national pride for the Polish even to this day. This is evident in the extensive memorial that exists upon the battlefield itself.