Austria and France, having formed an alliance following the First Treaty of Versailles, seek to defeat the German allies in turn in 1757.

First, a major French force will sweep through Western Germany defeating and occupying Hanover, and the French will swing to attack Prussia from the west while Austria comes from the south.

France had began building up a large force known as the Army of Westphalia under Marshal Louis Charles d'Estrées.

The picture is dark for the small Kingdom of Prussia in spring 1757, with the Austrians mobilizing to attack Prussian-controlled soil and a combined French and Reichsarmee (German states) army under the Prince of Soubise approaching from the west.

The Reichsarmee is a collection of armies from the smaller German states that have banded together to heed the appeal of the Holy Roman Emperor Francis I against Frederick II.

The French, allied with Austria, Russia, Sweden and Saxony, invade Germany in April with two armies, altogether about one hundred thousand soldiers.

The French hope to draw the attention of Prussia, which is allied with Britain and Hanover, away from the Bohemian theater where Prussia and Austria will fight several battles this year (Lobositz, Prague, Kolin).

One of the two French armies under the command of Soubise marches through central Germany  to join the imperial coalition army commanded by Prinz von Hildburghausen, which will have a disastrous encounter with a Prussian army at the Battle of Rossbach on November 5, 1757.

The other French army, commanded by the Duc d'Estrées, consisting of about fifty thousand infantry, ten thousand cavalry and sixty-eight cannons, advances towards the Electorate of Hanover.

As Prussia is heavily involved with its enemies Austria, Russia and Sweden and will therefore be unable able to help on the western front, this task is given to the Hanoverian Army of Observation, which has little support from Prussia, namely six Prussian battalions.

The main part of the  Hanoverian Army of Observation—about sixty percent—comes from Hanover and about twenty-five percent from Hesse, with smaller additional forces from Brunswick and Prussia.

The total strength of the Hanoverian Army of Observation consists of about thirty thousand infantry, five thousand cavalry and twenty-eight guns.

Hanover refuses to defend the Rhine, which is west of the Weser.

This leaves the Prussians no choice but to abandon their fortress in Wesel and to give up the line of the Lippe in April.

The French army begins to advance towards Hanover in early June 1757, once it becomes clear that there is to be no negotiated agreement.

The first skirmish between the two forces had taken place on May 3.

Part of the French army had been delayed by the Siege of Geldern, which took three months to capture from its Prussian garrison of eight hundred.

The bulk of the French army advances across the Rhine, progressing slowly because of the difficulties of logistics for moving an army estimated at around one hundred thousand.

Cumberland, whose main objective is preventing the occupation of Hanover, first concentrates his army at Bielefeld; ...

...then, after a brief stand in Brackwede, ...

...Cumberland decides to cross the Weser south of Minden into the territory of the Electorate of Hanover itself, while he tries to ready his troops.

The main idea is to use the Weser as a natural defense line and to make it impossible for the French troops to cross the river.

Cumberland deploys his main forces at Hameln, which is a couple of kilometers to the northwest of Hastenbeck, and leaves the Prussian battalions as garrison forces in Minden.

He also deploys small patrols all along the Weser.

The French meanwhile send a detachment to the north to capture the Prussian port of Emden, which is an important access point for Britain to Europe.

Emden falls on July 2 before a Royal Navy squadron sent to relieve it can reach here.

This cuts Hanover off from the Dutch Republic, meaning that supplies from Britain can now only be shipped direct by sea.

A strong French advance guard crosses the river Weser close to the town of Beverungen during the night of July 7.

The river Weser normally cannot easily be forded, but during the summer the water level drops down to a low of eighty centimeters (about three feet) between Münden and Hameln, making it possible for infantry and cavalry to cross.

The French advance troops now march to the north and establish a bridgehead at Höxter.

The French had sent another detachment to the south, which takes Kassel on July 15, securing their right flank.

The main army crosses the Weser on July 16, leaving the Duke of Cumberland no choice but to deploy his troops south of Hameln and to engage d'Estrées.

The Prussian battalions are now recalled by Frederick the Great, after losing the Battle of Kolin against Austria.