It is true that now, as so often before, Frederick underrated the firmness of the Queen. He was further disappointed by the unyielding attitude of Augustus, who possessed a dangerous patron in the Czarina. But England, the paymaster of the coalition, had no stomach for a war of vengeance against Prussia. To her the Austrian alliance was merely an investment. It would be profitable only if it produced hard fighting against her real foes, the French. Fontenoy, where the Sea Powers had been left to do their own fighting, shook her faith in her Hapsburg ally, and the conduct of the Eastern campaign showed that the Queen’s thoughts centred on the recovery of the province which England had induced her to give up. At this juncture England herself was attacked. The invasion of the Pretender compelled her to recall her troops from the Continent and favoured the convention which was concluded at Hanover towards the end of August. By the Convention of Hanover, signed on the 26th August, 1745, Frederick a third time deserted the French. He promised to vote for Francis at the Imperial election on condition that Silesia should be guaranteed to him by all Europe, while George II. undertook to induce Austria to renew the Treaty of Berlin within six weeks. The good offices of England, which as usual consisted in pressing the Queen to buy off her enemies, were entirely useless. At the end of August Austria and Saxony drew closer together, and on September 13th the House of Hapsburg regained its old prestige by the election of Francis as Emperor. Soon afterwards Frederick perceived that he had exhausted the supplies of north-eastern Bohemia and began to retire towards Silesia. By the end of September he had crossed the Elbe and encamped with 18,000 men at the foot of the mountains near the village of Soor. There something like his own manœuvre of Hohenfriedberg was practised upon him by Prince Charles with an army almost double the size of Frederick’s. Under cover of darkness the Austrians took up positions commanding the Prussian camp. Only the King’s swift grasp of the situation and the wonderful skill and speed of his troops averted a great disaster. In a five hours’ fight the Austrians were driven off, leaving more than 4000 men on the field and more than 3000 in the enemy’s hands. The number of Prussian casualties exceeded 3000—a heavy price to pay for bad scouting. Frederick was, moreover, put to great inconvenience by the sack of his camp and the capture of his secretary, the silent, assiduous Eichel.