Complex sentence: During much of the Cold War period, relations between the Republic of India and the erstwhile Imperial State of Iran suffered due to different political interests--non-aligned India fostered strong military links with the Soviet Union while Iran enjoyed close ties the United States.
Split into simpler sentences: During much of the Cold War period, relations between the Republic of India and the erstwhile Imperial State of Iran suffered due to different political interests. Non-aligned India fostered strong military links with the Soviet Union while Iran enjoyed close ties the United States.