The Convention of Klosterzeven (or the Convention of Kloster-Zeven) was a 1757 convention

Treaty

A treaty is an express agreement under international law entered into by actors in international law, namely sovereign states and international organizations. A treaty may also be known as an agreement, protocol, covenant, convention or exchange of letters, among other terms...

 signed at Klosterzeven between France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 and the Electorate of Hanover

Electorate of Hanover

The Electorate of Brunswick-Lüneburg was the ninth Electorate of the Holy Roman Empire of the German Nation...

 during the Seven Years' War

Seven Years' War

The Seven Years' War was a global military war between 1756 and 1763, involving most of the great powers of the time and affecting Europe, North America, Central America, the West African coast, India, and the Philippines...

 that led to Hanover's withdrawal from the war and partial occupation by French forces. It came in the wake of the Battle of Hastenbeck

Battle of Hastenbeck

The Battle of Hastenbeck was fought as part of the Invasion of Hanover during the Seven Year's War between the allied forces of Hanover, Hesse-Kassel and Brunswick and the French...

 in which Hanover had suffered a devastating defeat. Following the battle the Army of Observation had retreated northwards until it had reached Stade

Stade

Stade is a city in Lower Saxony, Germany and part of the Hamburg Metropolitan Region . It is the seat of the district named after it...

.

The agreement was deeply unpopular with Hanover's ally Prussia

Prussia

Prussia was a German kingdom and historic state originating out of the Duchy of Prussia and the Margraviate of Brandenburg. For centuries, the House of Hohenzollern ruled Prussia, successfully expanding its size by way of an unusually well-organized and effective army. Prussia shaped the history...

 whose Western frontier was severely weakened by the agreement. After the Prussian victory at Rossbach

Battle of Rossbach

The Battle of Rossbach took place during the Seven Years' War near the village of Roßbach, in the Electorate of Saxony. Frederick the Great defeated the allied armies of France and the Holy Roman/Austrian Empire...

 on 5 Nov 1757, King George II

George II of Great Britain

George II was King of Great Britain and Ireland, Duke of Brunswick-Lüneburg and Archtreasurer and Prince-elector of the Holy Roman Empire from 11 June 1727 until his death.George was the last British monarch born outside Great Britain. He was born and brought up in Northern Germany...

 was encouraged to disavow the treaty. Under pressure from Frederick the Great and William Pitt, the convention was subsequently revoked and Hanover re-entered the war the following year. The Duke of Cumberland who had signed the agreement on behalf of Hanover was disgraced when he returned to Britain ending his previously distinguished military career. He was replaced as commander by Duke Ferdinand of Brunswick

Duke Ferdinand of Brunswick

Ferdinand, Prince of Brunswick-Lüneburg , was a Prussian field marshal known for his participation in the Seven Years' War...

.