After a brief spell as a conservative, he crossed the floor to join the Liberals, then in power, who quickly recognised his potential, making him president of the Board of Trade in 1908. By 1914 he was First Lord of the Admiralty, where he can take credit for preparing the Navy for the outbreak of war. However, the failure of the Gallipoli campaign led to his demotion, and by the end of 1915 he had resigned. After a brief spell of active service on the western front, he was recalled by Lloyd George, who made him Minister of Munitions, a job that Churchill carried out with great energy and success.
After the war, the Liberal party began its dramatic decline. Churchill lost his seat in 1922, and when he was re-elected the following year it was as a Conservative. The new Prime Minister, Stanley Baldwin, immediately appointed him Chancellor of the Exchequer, a post that did not really suit Churchill, but that gave him a claim to succeed when Baldwin retired. His claim failed. This combined with his opposition to Indian Home Rule to exclude him from the Conservative Front Bench for the next ten years.
At first he was an isolated figure, but his opposition to Hitler after 1933 began to revive his career. By the time war broke out in 1939, Churchill had established himself as an essential part of any war cabinet, and he was recalled to the government, once again as First Lord of the Admiralty. Once again, his time at the Admiralty saw mixed success. He was largely responsible for the failed campaign in Norway (1940), but fortunately managed to avoid any blame. Instead, the political crisis caused by this failure saw Churchill finally achieve his life long ambition, becoming Prime Minister in May 1940.
This was just in time for the greatest crisis in British history. Hitler's armies overran France in a shatteringly short period, leaving Britain standing alone. Churchill's oratory and determination played a crucial role in keeping the war going, denying Hitler an easy victory and domination of Europe. He gave a series of inspirational speeches finally tuned to the needs of the day. Frustrated by Britain's resistance, Hitler turned his attention to Russia, relieving the pressure on Britain (and Churchill). Once Pearl Harbour brought America into the war, allied victory was assured.
Victory in the Second World War was not matched by political success. Churchill was heavily defeated in the 1945 election, a very heavy blow, but one that he recovered from. In 1946 he gave a speech warning about the danger from Soviet Russia, famous for his use of the 'Iron curtain'.
He remained Conservative leader, winning the 1951 election. Despite his age, he remained Prime Minister until 1955. He finally retired from the House of Commons in 1964, dying early the following year. Many felt that an era of British greatness died with Churchill.