Sir Winston Leonard Spencer-Churchill (30 November 1874 – 24 January 1965) was a British politician, army officer, and writer, who served as Prime Minister of the United Kingdom from 1940 to 1945 and again from 1951 to 1955. As a Member of Parliament (MP), he represented five constituencies during his career. As Prime Minister, Churchill oversaw British victory in the Second World War. Ideologically an economic liberal and British imperialist, he was a member of the Liberal Party from 1904 to 1924 before joining the Conservative Party, which he led from 1940 to 1955.
Born in Oxfordshire to an aristocratic family, Churchill was the son of an English politician and an American socialite. Joining the British Army, he saw action in British India, the Anglo–Sudan War, and the Second Boer War, gaining fame as a war correspondent and writing books about his campaigns. Elected an MP in 1900, initially as a Conservative, he defected to the Liberals in 1904. In H. H. Asquith's Liberal government, Churchill served as President of the Board of Trade, Home Secretary, and First Lord of the Admiralty. During the First World War, he oversaw the Gallipoli Campaign; after it proved a disaster, he resigned from government. He briefly resumed active army service on the Western Front as a battalion commander in the Royal Scots Fusiliers. Rejoining the Conservatives, he returned to government under David Lloyd George as Minister of Munitions, Secretary of State for War, Secretary of State for Air, then Secretary of State for the Colonies. After two years out of Parliament, he served as Chancellor of the Exchequer in Stanley Baldwin's Conservative government, returning the pound sterling in 1925 to the gold standard at its pre-war parity, a move widely seen as creating deflationary pressure on the UK economy.
Out of office during the 1930s, Churchill took the lead in calling for British rearmament to counter the growing threat from Nazi Germany. At the outbreak of the Second World War, he was re-appointed First Lord of the Admiralty. Following Prime Minister Neville Chamberlain's resignation in 1940, Churchill replaced him. Churchill oversaw British involvement in the Allied war effort, resulting in victory in 1945. After the Conservative's defeat in the 1945 general election, he became Leader of the Opposition. Amid the developing Cold War with the Soviet Union, he publicly warned of an "iron curtain" of Soviet influence in Europe and promoted European unity. He was re-elected prime minister in the 1951 election. His second term was preoccupied with foreign affairs, including the Malayan Emergency, Mau Mau Uprising, Korean War and a UK-backed Iranian coup. Domestically his government emphasised house-building and developed an atomic bomb. In declining health, Churchill resigned as prime minister in 1955, although remained an MP until 1964. Upon his death in 1965, he was given a state funeral.
Widely considered one of the 20th century's most significant figures, Churchill remains popular in the UK and wider Western world, where he is seen as a victorious wartime leader who played an important role in defending liberal democracy from the spread of fascism. He was decorated with a wide range of awards, including the 1953 Nobel Prize in Literature. Conversely, he was accused of warmongering and human rights abuses and his imperialist and racist views—coupled with actions surrounding the Bengal famine of 1943 and suppression of anti-imperialist movements—have generated considerable controversy.