The Battle of Grand Gulf was fought on April 29, 1863, during th: For general elections (elections to the House of Commons), the UK is currently divided into 650 constituencies, each of which is represented by one member of Parliament (MP) elected by the first-past-the-post system.[171] MPs hold office for up to five years and must then stand for re-election if they wish to continue to be an MP.[171] The Conservative Party, colloquially known as the Tory Party or the Tories, and the Labour Party have been the dominant political parties in the UK since the 1920s, leading to the UK being described as a two-party system. However, since the 1920s other political parties have won seats in the House of Commons, although never more than the Conservatives or Labour.[172]