In 1779 Aga Muhammad Khan Qajar, leader of the Qajars, conquered most of Iran. In the twentieth century a number of Iranian intellectuals, thinking that a parliament could protect national interests from the foreign imperialists who exercised so much influence over the Qajar shahs, organized a movement for a constitutional monarchy. In the mid-1970s Iran's economy seemed to prosper from the high price that Europe, Japan, and the United States paid for Iranian oil. By First World War Great Britain's interest in Iran intensified; the British navy had begun to switch from coal to oil fuel, much of which was obtained from the British-owned Anglo Persian Oil Company's Iranian wells at secretly lowered prices. The central themes of Islamic fundamentalism included the concept that Islamic religious rules and moral principles must be integrated with government and influence all aspects of society.