The Thousand Days' War (Spanish: Guerra de los Mil Días) was a civil war fought in Colombia from 17 October 1899 to 21 November 1902, at first between the Liberal Party and the government led by the National Party, and later – after the Conservative Party had ousted the National Party – between the liberals and the conservative government. Caused by the longstanding ideological tug-of-war of federalism versus centralism between the liberals, conservatives, and nationalists of Colombia following the implementation of the Constitution of 1886 and the political process known as the Regeneración (es), tensions reached a fever pitch after the presidential election of 1898, and in 17 October 1899, official insurrection against the National government was announced by members of the Liberal Party