The siege of Marienburg was an unsuccessful two-month siege of the castle in Marienburg (Malbork), the capital of the monastic state of the Teutonic Knights. The joint Polish and Lithuanian forces, under command of King Władysław II Jagiełło and Grand Duke Vytautas, besieged the castle between 26 July and 19 September 1410 in a bid of complete conquest of Prussia after the great victory in the Battle of Grunwald (Tannenberg). However, the castle withstood the siege and the Knights conceded only to minor territorial losses in the Peace of Thorn (1411). Marienburg defender Heinrich von Plauen is credited as the savior of the Knights from complete annihilation. Background Allied Polish and Lithuanian forces invaded Prussia in July 1410 with a goal of capturing Marienburg. Their path was blocked by the Teutonic Knights, who engaged the allied forces in the decisive Battle of Grunwald on 15 July 1410. The Knights suffered a great defeat, leaving most of their leadership dead or captured. The victorious Polish and Lithuanian forces stayed on the battlefield for three days; during this time Heinrich von Plauen, Komtur of Schwetz (Świecie), organized defense of Marienburg. Von Plauen did not participate in the battle and was trusted to command reserve forces of about 3,000 men in Schwetz. It is not entirely clear whether von Plauen marched to Marienburg based on pre-battle instructions of Grand Master Ulrich von Jungingen or on his own initiative to fill the leadership void. As the Polish–Lithuanian forces moved on to Marienburg, three Teutonic fortresses – Hohenstein (Olsztynek), Osterode (Ostróda), and Christburg (Dzierzgoń) – surrendered without resistance. The allied forces moved slowly, averaging only about per day, giving time for von Plauen to organize the defense. This delay has been criticized by modern historians as one of the greatest Polish–Lithuanian tactical mistakes and has been a subject of much speculation. Polish historian Paweł Jasienica suggested, for example, that Jagiełło might have intentionally given the Knights time to regroup, to keep the Order humbled but not decimated so as to not upset the balance of power between Poland (which would most likely acquire most of the Order possessions if it was totally defeated) and Lithuania; but a lack of primary sources precludes a definitive explanation. Siege The main Polish–Lithuanian forces arrived only on 26 July 1410. The day before von Plauen ordered the town outside the Marienburg Castle to be burned, depriving allied soldiers of