Reza Shah Pahlavi's rule from 1925 to 1941 in Iran was marked by significant modernization efforts and the establishment of an authoritarian regime. His government emphasized nationalism, militarism, secularism, and anti-communism, alongside strict censorship and propaganda.^[67] He introduced numerous socio-economic reforms, including reorganizing the army, government administration, and finances.^[68] Reza Shah's reign was a complex period of significant modernization and authoritarian rule, marked by both achievements in infrastructure and education and criticisms for oppression and political suppression.

To his supporters, Reza Shah's reign was seen as a period of significant progress, characterized by the introduction of law and order, discipline, central authority, and modern amenities like schools, trains, buses, radios, cinemas, and telephones.^[69] However, his rapid modernization efforts faced criticism for being "too fast"^[70] and "superficial,"^[71] with some viewing his reign as a time marked by oppression, corruption, excessive taxation, and a lack of authenticity. His rule was also likened to a police state due to its stringent security measures.^[69] His policies, especially those conflicting with Islamic traditions, caused discontent among devout Muslims and the clergy, leading to significant unrest, such as the 1935 rebellion at the Imam Reza shrine in Mashhad.^[72]

During Reza Shah's 16-year rule, Iran witnessed significant development and modernization. Major infrastructure projects were undertaken, including extensive road construction and the building of the Trans-Iranian Railway. The establishment of the University of Tehran marked the introduction of modern education in Iran.^[73] Industrial growth was substantial, with a 17-fold increase in the number of modern industrial plants, excluding oil installations. The country's highway network expanded from 2,000 to 14,000 miles.^[74]

Reza Shah dramatically reformed the military and civil services, founding a 100,000-man army,^[75] transitioning from reliance on tribal forces, and establishing a 90,000-man civil service. He set up free, compulsory education for both males and females and shut down private religious schools—Islamic, Christian, Jewish, etc.^[76] Additionally, he utilized funds from wealthy shrine endowments, notably in Mashhad and Qom, for secular purposes such as education, healthcare, and industrial projects.^[77]

Reza Shah's rule coincided with the Women's Awakening (1936–1941), a movement advocating for the removal of the chador in working society, arguing that it hindered women's physical activities and societal participation. This reform, however, faced resistance from religious leaders. The unveiling movement was closely linked to the Marriage Law of 1931 and the Second Congress of Eastern Women in Tehran in 1932.

In terms of religious tolerance, Reza Shah was notable for showing respect to the Jewish community, being the first Iranian monarch in 1400 years to pray in a synagogue during his visit to the Jewish community in Isfahan. This act significantly boosted the self-esteem of Iranian Jews and led to Reza Shah being highly regarded among them, second only to Cyrus the Great. His reforms allowed Jews to pursue new occupations and move out of ghettos.^[78] However, there were also claims of anti-Jewish incidents in Tehran in 1922 during his rule.^[79]

Historically, the term "Persia" and its derivatives were commonly used in the Western world to refer to Iran. In 1935, Reza Shah requested that foreign delegates and the League of Nations adopt "Iran" – the name used by its native people and meaning "Land of the Aryans" – in formal correspondence. This request led to the increased use of "Iran" in the Western world, altering the common terminology for the Iranian nationality from "Persian" to "Iranian." Later, in 1959, the government of Shah Mohammad Reza Pahlavi, Reza Shah Pahlavi's son and successor, declared that both "Persia" and "Iran" could officially be used interchangeably. Despite this, the use of "Iran" continued to be more prevalent in the West.

In foreign affairs, Reza Shah sought to diminish foreign influence in Iran. He made significant moves, such as canceling oil concessions with the British and seeking alliances with countries like Turkey. He balanced foreign influence, notably between Britain, the Soviet Union, and Germany.^[80] However, his foreign policy strategies collapsed with the onset of World War II, leading to the Anglo-Soviet invasion of Iran in 1941 and his subsequent forced abdication.^[81]