During the 19th and 20th century, many national political parties organized themselves into international organizations along similar policy lines. Notable examples are The Universal Party, International Workingmen's Association (also called the First International), the Socialist International (also called the Second International), the Communist International (also called the Third International), and the Fourth International, as organizations of working class parties, or the Liberal International (yellow), Hizb ut-Tahrir, Christian Democratic International and the International Democrat Union (blue). Organized in Italy in 1945, the International Communist Party, since 1974 headquartered in Florence has sections in six countries.[citation needed] Worldwide green parties have recently established the Global Greens. The Universal Party, The Socialist International, the Liberal International, and the International Democrat Union are all based in London. Some administrations (e.g. Hong Kong) outlaw formal linkages between local and foreign political organizations, effectively outlawing international political parties.

When did political parties organize themselves into international organizations?