The British seized Baghdad in March 1917. In 1918 it was joined to Mosul and Basra in the new nation of Iraq using a League of Nations Mandate. Experts from India designed the new system, which favoured direct rule by British appointees, and demonstrated distrust of the aptitude of local Arabs for self-government. The old Ottoman laws were discarded and replaced by new codes for civil and criminal law, based on Indian practice. The Indian rupee became the currency. The army and police were staffed with Indians who had proven their loyalty to the British Raj. The large-scale Iraqi revolt of 1920 was crushed in the summer of 1920 but it was a major stimulus for Arab nationalism. The Turkish Petroleum Company was given a monopoly on exploration and production in 1925. Important oil reserves were First discovered in 1927; the name was changed to the Iraq Petroleum Company (IPC) in 1929. It was owned by a consortium of British, French, Dutch and American oil companies, and operated by the British until it was nationalized in 1972. The British ruled under the League mandate from 1918 to 1933. Formal independence was granted in 1933, but with a very powerful British presence in the background.