Edmund Ironside, 1st Baron Ironside in the context of "Occupation of Istanbul"

The Pahlavi dynasty (Persian: خاندان پهلوی) was an Iranian royal dynasty that was the last to rule Iran before the country's monarchy was overthrown by the Iranian Revolution in 1979. It was founded in 1925 by Reza Shah Pahlavi, a non-aristocratic Iranian soldier of Mazanderani origin, who took on the name of the Pahlavi scripts of the Middle Persian language from the Sasanian Empire of pre-Islamic Iran. The dynasty largely espoused this form of Iranian nationalism rooted in the pre-Islamic era (notably based on the Achaemenid Empire) during its time in power, especially under its last king Mohammad Reza Pahlavi.

The dynasty replaced the Qajar dynasty in 1925 after the 1921 coup d'état, beginning on 14 January 1921 when 42-year-old soldier Reza Khan was promoted by British General Edmund Ironside to lead the British-run Persian Cossack Brigade. About a month later, under British direction, Reza Khan's 3,000–4,000 strong detachment of the Cossack Brigade reached Tehran. The rest of the country was taken by 1923, and by October 1925 the Majlis agreed to depose and formally exile Ahmad Shah Qajar. The Majlis declared Reza Pahlavi as the Shah of Iran on 12 December 1925, pursuant to the Persian Constitution of 1906. Initially, Pahlavi had planned to declare the country a republic, as his contemporary Mustafa Kemal Atatürk had done in Turkey, but he abandoned the idea in the face of British and clerical opposition.

1921 Persian coup d'état, known in Iran as 3 Esfand 1299 coup d'état (Persian: کودتای ۳ اسفند ۱۲۹۹ with the Solar Persian date), refers to several major events in Qajar Persia in 1921, which eventually led to the deposition of the Qajar dynasty and the establishment of the Pahlavi dynasty as the ruling house of Iran in 1925.

The events began with a coup by the Persian Cossack Brigade headed by Reza Khan on 22 February 1921. The precise level of British involvement in the coup remains a matter of historical debate, but it is almost certain that Edmund Ironside provided advice to the plotters. With this coup Ziaoddin Tabatabaee took over power and became prime minister. The coup was largely bloodless and faced little resistance. With his expanded forces and the Cossack Brigade, Reza Khan launched successful military actions to eliminate separatist and dissident movements in Tabriz, Mashhad and the Jangalis in Gilan. The campaign against Simko and the Kurds was less successful and lasted well into 1922, though eventually concluding with Iranian success.