Tehran woke in heat and dust on 19 August 1953, and by midday the streets were full of shouted slogans, improvised weapons, and men climbing on lorries. A tank fired a single shell into Mohammad Mosaddegh’s house, and the prime minister of Iran, who had become the centre of the crisis, slipped from power after a day of violence in the capital.

It had begun long before that morning. Mosaddegh had risen through the National Front, won the confidence of the Majlis in 1951, and pushed through the nationalisation of Iran’s oil industry after the Anglo-Iranian Oil Company refused to audit its books and accept Iranian control. Britain answered with a worldwide boycott, an embargo on Iranian oil, and covert efforts to break his government.

The oil question was never just oil. The Abadan refinery, then the world’s largest, stood as a British-built prize on the Shatt al-Arab, and by 1951 thousands of workers had lost their jobs when production collapsed. Clement Attlee chose economic pressure over force; Winston Churchill, back in office in 1952, went further and asked the Eisenhower administration to help remove Mosaddegh.

Mosaddegh himself was no simple figurehead. He had been jailed by Reza Shah in 1940, which hardened his dislike of monarchy, and he believed the Shah should reign but not rule. Yet by 1952 and 1953 he was using emergency powers, arresting opponents, and in July 1953 he pushed through a referendum to dissolve parliament that won 2,043,300 votes to 1,300. His enemies called it fraudulent, and the Shah saw his authority slipping away.

The coup was planned by the United Kingdom and the United States under Operation Boot and TP-AJAX, also known as Operation Ajax. British intelligence pressed the case through MI6, while the CIA, led in the field by Kermit Roosevelt Jr., backed propaganda, bribery, and paid demonstrators. The Shah signed decrees dismissing Mosaddegh and appointing General Fazlollah Zahedi, then fled to Baghdad when the first attempt on 15 August faltered.

On 19 August the plot came together. CIA-backed crowds and pro-Shah groups flooded Tehran, some recruited from the city’s feared mobsters, others brought in by bus and truck. The Tudeh Party, which had infiltrated parts of the military, clashed in the streets, but by afternoon the army had seized government buildings. Mosaddegh fled, then surrendered to avoid further bloodshed. Between 200 and 300 people were killed.

After the coup, Zahedi formed a new government and Mohammad Reza Pahlavi ruled more firmly as Shah, with heavy American support. Mosaddegh was tried for treason, sentenced on 21 December 1953 to three years in jail, and then kept under house arrest for the rest of his life. His foreign minister, Hossein Fatemi, was executed in 1954, while the Shah’s security state grew into SAVAK, the secret police trained in part by Americans.