information:classification, linguistic:paraphrasing
Battle of Grunwald

When the war resumed in June 1410, Władysław advanced into the Teutonic heartland at the head of an army of about 20,000 mounted nobles, 15,000 armed commoners, and 2,000 professional cavalry mainly hired from Bohemia. After crossing the Vistula over the pontoon bridge at Czerwińsk, his troops met up with those of Vytautas, whose 11,000 light cavalry included Lithuanians, Ruthenians, and Tatars. The Teutonic Order's army had about 18,000 cavalry, mostly Germans, and 5,000 infantry. On 15 July, at the Battle of Grunwald after one of the largest and most ferocious battles of the Middle Ages, the allies won a victory so overwhelming that the Teutonic Order's army was virtually annihilated, with most of its key commanders killed in combat, including Grand Master Ulrich von Jungingen and Grand Marshal Friedrich von Wallenrode. Thousands of troops were reportedly slaughtered on either side.

The road to the Teutonic capital Marienburg now lay open, the city undefended; but for reasons the sources do not explain, Władysław hesitated to pursue his advantage. On 17 July, his army began a laboured advance, arriving at Marienburg only on 25 July, by which time the new Grand Master, Heinrich von Plauen, had organised a defence of the fortress. The apparent half-heartedness of the ensuing siege, called off by Władysław on 19 September, has been variously ascribed to the impregnability of the fortifications, high Lithuanian casualties, to Władysław's unwillingness to risk further casualties, or to his desire to keep the Order weakened but undefeated 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 sources precludes a definitive explanation.