Why did Mosaddeq nationalize the Iranian oil industry in 1951?

Prime Minister Mohammed Mosaddeq received approval from the majlis (parliament) to nationalize the Iranian oil industry after Iranian governments to that point had failed to re-negotiate an equitable revenue sharing agreement with British and U.S. oil companies. The decision meant that the considerable revenue now went to the Iranian government and could be spent on local social and economic programs rather than going to the British government and privately owned oil companies. But it was a decision that Britain and the U.S.A. would not take lying down. This source-based activity is designed for students of the NSW Modern History Syllabus for the Australian Curriculum.
Higher School Certificate course
National Studies
Option H: Iran 1953-1989