Battle of Grunwald
He made no mention of the Lithuanians, who later returned to the battlefield. Thus Długosz portrayed the battle as a single-handed Polish victory. This view contradicted Cronica conflictus and has been challenged by modern historians.
Starting with an article by Vaclaw Lastowski in 1909, they proposed that the retreat had been a planned maneuver borrowed from the Golden Horde. A feigned retreat had been used in the Battle of the Vorskla River (1399), when the Lithuanian army had been dealt a crushing defeat and Vytautas himself had barely escaped alive. This theory gained wider acceptance after the discovery and publication, in 1963 by Swedish historian Sven Ekdahl, of a German letter. Written a few years after the battle, it cautioned the new Grand Master to look out for feigned retreats of the kind that had been used in the Great Battle. Stephen Turnbull asserts that the Lithuanian tactical retreat did not quite fit the formula of a feigned retreat; such a retreat was usually staged by one or two units (as opposed to almost an entire army) and was swiftly followed by a counterattack (whereas the Lithuanians had returned late in the battle).

Battle continues: Polish–Teutonic fight: While the Lithuanians were retreating, heavy fighting broke out between Polish and Teutonic forces. Commanded by Grand Komtur Kuno von Lichtenstein, the Teutonic forces concentrated on the Polish right flank. Six of von Walenrode's banners did not pursue the retreating Lithuanians, instead joining the attack on the right flank. A particularly valuable target was the royal banner of Kraków. It seemed that the order were gaining the upper hand, and at one point the royal standard-bearer, Marcin of Wrocimowice, lost the Kraków banner. However, it was soon recaptured and fighting continued. Władysław II Jagiełło deployed his reserves—the second line of his army. Grand Master Ulrich von Jungingen then personally led 16 banners, almost a third of the original Teutonic strength, to the right Polish flank, and Władysław II Jagiełło deployed his last reserves, the third line of his army. The melee reached the Polish command and one knight, identified as Lupold or Diepold of Kökeritz, charged directly against King Władysław II Jagiełło. Władysław's secretary, Zbigniew Oleśnicki, saved the king's life, gaining royal favor and becoming one of the most influential people in Poland.

Battle ends: Teutonic Order defeated: At that time the reorganized Lithuanians returned to the battle, attacking von Jungingen from the rear. The Teutonic forces were by then becoming outnumbered by the mass of Polish knights and advancing Lithuanian cavalry. As von Jungingen attempted to break through the Lithuanian lines, he was killed. According to Cronica conflictus, Dobiesław of Oleśnica thrust a lance through the Grand Master's neck, while Długosz presented Mszczuj of Skrzynno as the killer. Surrounded and leaderless, the Teutonic Order began to retreat. Part of the routed units retreated towards their camp. This move backfired when the camp followers turned against their masters and joined the manhunt. The knights attempted to build a wagon fort: the camp was surrounded by wagons serving as an improvised fortification. However, the defense was soon broken and the camp was ravaged. According to Cronica conflictus, more knights died there than on the battlefield. The battle lasted for about ten hours.
The Teutonic Order attributed the defeat to treason on the part of Nicholas von Renys (Mikołaj of Ryńsk), commander of the Culm (Chełmno) banner, and he was beheaded without a trial. He was the founder and leader of the Lizard Union, a group of knights sympathetic to Poland. According to the order, von Renys lowered his banner, which was taken as a signal of surrender and led to the panicked retreat. The legend that the order was "stabbed in the back" was echoed in the post-World War I stab-in-the-back myth and preoccupied German historiography of the battle until 1945.

Aftermath: 

Casualties and captives: A note sent in August by envoys of King Sigismund of Hungary, Nicholas II Garai and Stibor of Stiboricz, put total casualties at 8,000 dead "on both sides". However, the wording is vague and it is unclear whether it meant a total of 8,000 or 16,000 dead. A papal bull from 1412 mentioned 18,000 dead Christians. In two letters written immediately after the battle, Władysław II Jagiełło mentioned that Polish casualties were small (paucis valde and modico) and Jan Długosz listed only 12 Polish knights who had been killed. A letter by a Teutonic official from Tapiau (Gvardeysk) mentioned that only half of the Lithuanians returned, but it is unclear how many of those casualties are attributable to the battle and how many to the later siege of Marienburg.
The defeat of the Teutonic Order was resounding. According to Teutonic payroll records, only 1,427 men reported back to Marienburg to claim their pay. Of 1,200 men sent from Danzig, only 300 returned. Between 203 and 211 brothers of the Order were killed, out of 270 that participated in battle, including much of the Teutonic leadership—Grand Master Ulrich von Jungingen, Grand Marshal Friedrich von Wallenrode, Grand Komtur Kuno von Lichtenstein, Grand Treasurer Thomas von Merheim, Marshal of Supply Forces Albrecht von Schwartzburg, and ten of the komturs. Marquard von Salzbach, Komtur of Brandenburg (Ushakovo) and Heinrich Schaumburg, voigt of Sambia, were executed by order of Vytautas after the battle. The bodies of von Jungingen and other high-ranking officials were transported to Marienburg Castle for burial on 19 July. The bodies of lower-ranking Teutonic officials and 12 Polish knights were buried at the church in Tannenberg. The rest of the dead were buried in several mass graves. The highest-ranking Teutonic official to escape the battle was Werner von Tettinger, Komtur of Elbing (Elbląg).
Polish and Lithuanian forces took several thousand captives. Among these were Dukes Konrad VII of Oels (Oleśnica) and Casimir V of Pomerania. Most of the commoners and mercenaries were released shortly after the battle on condition that they report to Kraków on 11 November 1410. Only those who were expected to pay ransom were kept. Considerable ransoms were recorded; for example, the mercenary Holbracht von Loym had to pay 150 kopas of Prague groschen, amounting to more than 30 kg (66 lb) of silver.

Further campaign and peace: After the battle, the Polish and Lithuanian forces delayed their attack on the Teutonic capital in Marienburg (Malbork), remaining on the battlefield for three days and then marching an average of only about 15 km (9.3 mi) per day. The main forces did not reach heavily fortified Marienburg until 26 July. This delay gave Heinrich von Plauen enough time to organize a defense. Władysław II Jagiełło also sent his troops to other Teutonic fortresses, which often surrendered without resistance, including the major cities of Danzig (Gdańsk), Thorn (Toruń), and Elbing (Elbląg). Only eight castles remained in Teutonic hands. The besiegers of Marienburg expected a speedy capitulation and were not prepared for a long siege, suffering from lack of ammunition, low morale, and an epidemic of dysentery. The order appealed to their allies for help, and Sigismund of Hungary, Wenceslaus, King of the Romans, and the Livonian Order promised financial aid and reinforcements.
The siege of Marienburg was lifted on 19 September. The Polish–Lithuanian forces left garrisons in the fortresses they had taken and returned home. However, the order quickly recaptured most of the castles. By the end of October only four Teutonic castles along the border remained in Polish hands. Władysław II Jagiełło raised a fresh army and dealt another defeat to the order in the Battle of Koronowo on 10 October 1410. Following other brief engagements, both sides agreed to negotiate.
The Peace of Thorn was signed in February 1411. Under its terms, the order ceded the Dobrin Land (Dobrzyń Land) to Poland and agreed to resign their claims to Samogitia during the lifetimes of Władysław II Jagiełło and Vytautas, although another two wars—the Hunger War of 1414 and the Gollub War of 1422—would be waged before the Treaty of Melno permanently resolved the territorial disputes. The Poles and Lithuanians were unable to translate the military victory into territorial or diplomatic gains.