Socialism in Iran or Iranian socialism is a political ideology that traces its beginnings to the 20th century and encompasses various political parties in the country. Iran experienced a short Third World Socialism period at the zenith of the Tudeh Party after the abdication of Reza Shah and his replacement by his son, Mohammad Reza Pahlavi (though the party never rose to power). After failing to reach power, this form of third world socialism was replaced by Mosaddegh's populist, non-aligned Iranian nationalism of the National Front party as the main anti-monarchy force in Iran, reaching power (1949–1953), and it remained with that strength even in opposition (after the overthrowing of Mossadegh) until the rise of Islamism and the Iranian Revolution. The Tudehs have moved towards basic socialist communism since then.