German rule began in mainland Tanzania during the late 19th century when Germany formed German East Africa. This was followed by British rule after World War I. The mainland was governed as Tanganyika, with the Zanzibar Archipelago remaining a separate colonial jurisdiction. Following their respective independence in 1961 and 1963, the two entities merged in 1964 to form the United Republic of Tanzania. The countries had joined the British Commonwealth in 1961 and Tanzania is still a member of the Commonwealth as one republic.