The term 'Iranian Leaders, Once' can be summarized by the crossword solution 'Shahs, ' which is a five-letter word. Shahs were the rulers of Iran from 1501 to 1979, when the monarchy was overthrown and replaced by an Islamic Republic. The title of Shah was used by the Persian emperors of the Achaemenid dynasty, the Parthian kings, and the Sassanid dynasty. The last Shah of Iran was Mohammad Reza Pahlavi, who was overthrown in the Iranian Revolution of 1979.