Galissonière. June 20 – A garrison of the British Army in India is imprisoned in the Black Hole of Calcutta. June 22 – The Coup of 1756, an attempted coup d'état planned by Queen Louisa Ulrika of Sweden, to abolish the rule of the Riksdag of the Estates and reinstate absolute monarchy in Sweden with the support of the Hovpartiet, is exposed and subdued. June 25 – The Marine Society is founded in London, the world's oldest seafarers' charity. June 29 – Seven Years' War: Siege of Fort St Philip at Port Mahón: The British garrison in Menorca surrenders to the French after two months' siege by the Duke of Richelieu. July–September July 30 – Bartolomeo Rastrelli presents the newly built Catherine Palace at Tsarskoye Selo to Empress Elizabeth of Russia and her court. August 14 – Seven Years' War: French and Indian War – Fort Oswego falls to the French. August 29 – Frederick II of Prussia invades Saxony, beginning the Third Silesian War within the Seven Years' War on the European continent. September 2 – Abu l-Hasan Ali I, Bey of Tunis is forcibly removed after 23 years as the ruler of the North African emirate by his cousins, who are avenging the overthrow and execution of their father, Husayn in 1735. Hasan Ali surrenders to the rebels and is imprisoned in Algiers, then executed on September 22 on orders of the new Bey of Tunis, Muhammad I ar-Rashid. October–December October 1 – Seven Years' War: Battle of Lobositz – Frederick defeats an Austrian army under Marshal Maximilian Ulysses, Reichsgraf von Browne. October 14 – An "Agreement of Friendship and Trade" is signed by Sultan Osman III and King Frederick V. Denmark appoints an extraordinary representative to the Ottoman Empire. November 16 – Thomas Pelham-Holles, the Duke of Newcastle, is forced to resign as Prime Minister of Great Britain after the British lose the Battle of Minorca to the French. The office of Prime Minister remains vacant for eight months with William Pitt and the Duke of Devonshire leading the cabinet. December – Seven Years' War – French and Indian War: Militias of the Royal Colony of North Carolina build a fort on the province's western frontier to protect it against natives allied with the French. The fort is named Fort Dobbs in honor of North Carolina Governor Arthur Dobbs, who persuaded the North Carolina legislature to fund