Faced with an army mutiny and violent demonstrations against his rule, Mohammad Reza Shah Pahlavi is forced to flee the country. Pahlevi was 22 when he inherited his father's title of shah of Iran in 1941. Although he sought to modernize Iran, Pahlevi clung to traditions that seemed to suit an ancient Persian monarch. In 1971, he held an extravagant celebration of the 2,500th anniversary of the pre-Islamic Persian monarchy, and in 1976, formally replaced the Islamic calendar with a Persian calendar. Discontent among fundamentalist Muslims grew, and the shah became more repressive, using his brutal secret police force to suppress opposition. His alienation of religious leaders, repressive policies, and close relations with the United States became a rallying cry for the Islamic fundamentalist movement of the Ayatollah Khomeini. After fleeing Iran, the shah traveled to several countries before entering the United States in 1979 for medical treatment of his cancer. In Tehran, Islamic militants responded by storming the U.S. embassy and taking the staff hostage. Backed by Khomeini, the militants demanded the return of the shah to Iran to stand trial for his crimes. The U.S. refused to turn over the shah and 52 American hostages were held for 444 days. They were finally released in early 1981 following successful negotiations conducted through Algerian intermediaries. The shah died in Egypt in July 1980.