Imam Khomeini, who was strongly opposed to the "capitulations" and diplomatic immunity granted to American military personnel in Iran by the Shah regime in 1960s, became under the scrutiny of the Shah regime and its western backers.
Under Imam’s unprecedented leadership, the struggle for the Islamic Revolution was being boosted day by day and people were rallying around him.
So the Shah regime was trembling and felt fears and decided to send Imam exile where he spent about 15 years. But he never gave up struggle and kept monitoring the Revolution from abroad until historic victory in 1979.