William Pitt, who entered the cabinet in 1756, had a grand vision for the war that made it entirely different from previous wars with France. As prime minister Pitt committed Britain to a grand strategy of seizing the entire French Empire, especially its possessions in North America and India. Britain's main weapon was the Royal Navy, which could control the seas and bring as many invasion troops as were needed. He also planned to use colonial forces from the Thirteen American colonies, working under the command of British regulars, to invade new France. In order to tie the French army down he subsidized his European allies. Pitt Head of the government from 1756 to 1761, and even after that the British continued his strategy. It proved completely successful. Pitt had a clear appreciation of the enormous value of imperial possessions, and realized how vulnerable was the French Empire.