failure. Britain's attempts to take the offensive in North America had ended in disaster, Menorca had been lost, and the Duke of Cumberland's Army of Observation was retreating across Hanover following the Battle of Hastenback. In October Cumberland was forced to conclude the Convention of Klosterzeven, which would take Hanover out of the war. The French Invasion of Hanover posed a threat to Britain's ally Prussia, which was now vulnerable to attack from the west by the French as well as facing attack from Austria, Russia, Saxony and Sweden. Although it was late in the campaigning season when he had come to power, Pitt set about trying to initiate a more assertive strategy. He conspired with a number of figures to persuade the Hanoverians to revoke the Klosterzevern Convention and re-enter the war on Britain's side, which they did in late 1757. He also put into practice a scheme of Naval Descents that would make amphibious landings on the French coast. The first of these, the Raid on Rochefort, took place in September but was not a success. The centrepiece of the campaign in North America, an expedition to capture Louisbourg, was aborted due to the presence of a large French fleet and a gale that scattered the British fleet. 1758 In 1758 Pitt began to put into practice a new strategy to win the Seven Years' War, which would involve tying down large numbers of French troops and resources in Germany, while Britain used its naval supremacy to launch expeditions to capture French forces around the globe. Following the capture of Emden he ordered the dispatch of the first British troops to the European continent under the Duke of Marlborough, who joined Brunswick's army. This was a dramatic reversal of his previous position, as he had recently been strongly opposed to any such commitment. Pitt had been lobbied by an American merchant Thomas Cumming to launch an expedition against the French trading settlements in West Africa. In April 1758 British forces captured the ill-defended fort of Saint-Louis in Senegal. The mission was so lucrative that Pitt sent out further expeditions to capture Gorée and Gambia later in the year. He also drew up plans to attack French islands in the Caribbean the following year at the suggestion of a Jamaican sugar planter William Beckford. In North America, a second British attempt to capture Louisbourg succeeded. However, Pitt's pleasure over