In the second week of June 1410, only eleven days before the armistice was due to end, Ulrich von Jungingen asked for the armistice to be extended until July 4 to let the mercenaries from Western Europe arrive. In their words "the knights from other nations of Europe wished to participate in the crusade, and that honor should not be denied to them." Since those were times when honor and chivalry were in high regard the extension was given.
On 30 June 1410, the forces of Greater Poland and Lesser Poland surprised Teutonic Knights by crossing the Vistula River over a pontoon bridge, something that was rarely done in medieval Europe, and joined with the forces of Masovia and the Grand Duchy of Lithuania. The Polish and Lithuanian forces assembled on 2 July 1410. A week later they crossed the border into the Teutonic Knights territory, heading for the enemy’s main castle in Marienburg (Malbork). The Teutonic Knights were caught by surprise.
