Following World War II, nationalistic sentiments were on the rise in the Middle East; most notable being Iranian nationalism, and Arab Nationalism. In Iran, the AIOC and the pro-western Iranian government led by Prime Minister Ali Razmara resisted nationalist calls to revise AIOC's concession terms in Iran's favour. In March 1951, Razmara was assassinated and Mohammed Mossadeq, a nationalist, was elected as the new prime minister by the Majlis of Iran (parliament). In April 1951, the Iranian government nationalised the Iranian oil industry by unanimous vote, and the National Iranian Oil Company (NIOC) was formed, displacing the AIOC. The AIOC withdrew its management from Iran, and Britain organized an effective worldwide embargo of Iranian oil. The British government, which owned the AIOC, contested the nationalisation at the International Court of Justice at The Hague, but its complaint was dismissed.
Prime Minister Churchill asked President Eisenhower for help in overthrowing Mossadeq. The anti-Mossadeq plan was orchestrated under the code-name 'Operation Ajax' by CIA, and 'Operation Boot' by SIS (MI6). The CIA and the British helped stage a coup in August 1953, the 1953 Iranian coup d'état, which established pro-Western general Fazlollah Zahedi as the new PM, and greatly strengthened the political power of Shah Mohammad Reza Pahlavi. The AIOC was able to return to Iran.