Reza Shah Pahlavi was a military brigadier general, minister of war, prime minister, first Shah of the House of Pahlavi of the Imperial State of Iran. He reigned from 15 December 1925 until he was forced to abdicate by the Anglo-Soviet invasion of Iran on 16 September 1941. Reza Shah introduced many social, economic, and political reforms during his reign, ultimately laying the foundation of the modern Iranian state. Therefore, he is regarded as the founder of modern Iran.
At the age of 14 he joined the Cossack Brigade, and also served in the army. In 1911 he was promoted to First Lieutenant, by 1912 he was elevated to the rank of Captain and by 1915 he became a Colonel. In February 1921, as leader of the entire Cossack Brigade based in Qazvin he marched towards Tehran and seized the capital. He forced the dissolution of the government and installed Zia al-Din Tabatabaie as the new Prime Minister. Reza Khan's first role in the new government was Commander-in-Chief of the Army and the Minister of War.
Two years after the 1921 Persian coup d'état, led by Zia ol Din Tabatabaee, Reza Pahlavi became Iran's prime minister.