Complex sentence: In the late 1970s, the administration of U.S. President Jimmy Carter sought to improve relations between the U.S. and Cuba, though relations were strained when Cuba contributed troops to support the Soviet Union's military intervention in Africa and the Middle East.
Split into simpler sentences: In the late 1970s, the administration of U.S. President Jimmy Carter sought to improve relations between the U.S. and Cuba. However, relations were still strained because Cuba contributed troops to support the Soviet Union's military intervention in Africa and the Middle East.