After Emperor Napoleon I smashed the main Prussian armies at the Battle of Jena-Auerstedt on 14 October, his victorious Grande Armée chased his enemies across the Elbe River.

In September 1806, when King Frederick William III mobilized the Prussian armies, a substantial force assembled in or near the former Electorate of Hanover.

Lieutenant General Gebhard von Blücher concentrated 16 battalions of infantry and 17 squadrons of cavalry to the west at Paderborn, Osnabrück, Leer, and Oldenburg.

[2] This body became the westernmost field army and its 30,000 troops were placed under the command of General of Infantry Ernst von Rüchel and Blücher.

[3] The Prussian high command understood that Napoleon's major thrust must come from the south, so the western field army marched toward Erfurt at the beginning of October.

The small mobile forces were assembled near Münster and placed under the command of General Karl Ludwig von Lecoq.

Opposing the Prussians were King Louis Bonaparte in Holland and Marshal Édouard Adolphe Casimir Joseph Mortier at Mainz.

Napoleon planned to hold Louis and Mortier in place until he defeated the Prussian main army, at which time they would seize Hesse-Kassel and Hanover.

Hearing a report that French forces already blocked his path, he halted his march on the 27th and returned to Hamelin where he began acquiring food and supplies to sustain a siege.

He sent Oberst (Colonel) Christian Friedrich von der Osten with one dragoon regiment and one infantry battalion across the Elbe, where he joined a part of Blücher's command.

[5] After hearing of Jena-Auerstedt, General-Major Karl Anton Ernst von Bila left Hanover on 20 October with one battalion, the treasure, and the archives.

He met his younger brother General-Major Rudolf Ernst Christoph von Bila at Anklam on 31 October, but the next day they and their 2,200 troops surrendered to General of Division Nicolas Léonard Beker's dragoons.

The King of Holland was supposed to capture Paderborn and Münster, while the marshal was to seize Fulda and come into contact with General of Division Henri Jacques Guillaume Clarke at Erfurt.

Though William I, Elector of Hesse maintained an official neutrality, Napoleon knew that he was hostile to France and decided to depose him.

On the morning of 1 November, Mortier's force entered Kassel from the south while Louis' troops arrived from the north soon afterward.

[9] Mortier left Dumonceau 6,000 men and 12 cannons to blockade Hamelin,[8] while he continued on toward the city of Hanover, which he seized on 12 November.

The Frenchman reminded his enemies that there were no Prussian forces within 400 kilometers, then dropped his bombshell, the armistice agreement reached with Lucchesini.

The garrison of 629 fusiliers and men unfit for field duty was under the leadership of General-Major von Johann Adam Siegmund Uttenhoven.