The Battle of Heilsberg took place on 10 June 1807, during the Napoleonic Wars. Overview On 24 May 1807, the Siege of Danzig ended when Prussian General Friedrich Adolf, Count von Kalckreuth capitulated to French Marshal François Joseph Lefebvre. This gave Napoleon the opportunity to engage the Russian forces led by Levin August von Bennigsen. On 2 June, before Napoleon could act, Bennigsen ordered his columns to converge on Marshal Michel Ney's exposed VI Corps. Outnumbered by 63,000 to 17,000, Ney fought a rear guard action at the Battle of Guttstadt-Deppen on 5 and 6 June. Though he lost his baggage train, two guns, and 2,042 men, Ney managed to escape to the southwest over the Pasłęka (Passarge) River with the bulk of his soldiers. Within two days, Napoleon had ordered his 190,000-man army to close in on the 100,000 Russians and 15,000 Prussians. Aware of their approach, Bennigsen ordered his troops to fall back on Lidzbark Warmiński ("Heilsberg" in German). The Russian army took up strong defensive positions around the town, which stood on the Łyna (Alle) River. The French army, under Marshals Murat and Lannes, attacked on 10 June. Bennigsen repelled several attacks, resulting in huge French casualties, but had to withdraw towards Friedland the following day. Four days later, the decisive Battle of Friedland occurred, ending the War of the Fourth Coalition with the passing of the Treaty of Tilsit. Influences on the battle Geography The Battle of Heilsberg was fought on the Alle river, known today as the Lyna. The Teutonic Castle being the focal point of the battle was held by Russian control. Terrain Aside from geographical advantages, the Russians had also spent three to four months compiling tactics on how to defend against a French invasion, regardless of where they would attack the castlegrounds. Defensively, the castle was supported by its bridges and walls, both of which were built along the perimeter of the castle. The land surrounding the Teutonic Castle acted as an obstacle for the French army due to the increase of elevation from the base of the river to the castles foundation. The Prussian 21st Fusiliers, commanded by Ludwig August von Stutterheim, was garrisoned there. Climate Although the terrain was punishment enough for the French, weather also took a toll on their abilities and health. During the day, on top of the weight being carried in regards to supplies and armory,