1907  Introduction of constitution which limits the absolutist powers of rulers.

1914-1918  Iran declares neutrality but is scene of heavy fighting during World War I.

1921  Reza Khan, a military officer in Persia's Cossack Brigade, names himself shah of Persia after successfully staging a coup against the government of the Qajar Dynasty. He immediately launches an ambitious campaign to modernize the country. Among other plans, he hopes to develop a national public education system, build a national railroad system and improve health care.

1923  Reza Khan becomes prime minister.

1925  Ahmad Shah, the Qajar dynasty's final ruler, is deposed, and an assembly votes in Reza Khan (who had adopted the last name Pahlavi) as Persia's new shah.

1926  Reza Khan Pahlavi is crowned, marking the beginning of the Pahlavi Dynasty. The shah's eldest son, Mohammad Reza, is named crown prince.  

1935  Persia is officially renamed Iran. By the mid-'30s, Reza Khan's dictatorial approach begins to cause dissent.

1941  Although Reza Khan declares Iran a neutral power during World War II, Iran's British-controlled oil interests are largely maintained by German engineers and technicians, and Khan refuses to expel German citizens despite a request by Britain. In September 1941, following British and Soviet occupation of western Iran, Reza Shah is forced out of power. His son, Mohammad Reza Shah Pahlavi, succeeds him on the throne.

1949  An attempt on the shah's life, attributed to the pro-Soviet Tudeh Party, results in an expansion of the Mohammad Reza Shah Pahlavi's constitutional powers.