Complex sentence: Truman had touched upon one of the most sensitive issues in civil-military relations in the post-World War II period: civilian control of nuclear weapons, which was enshrined in the Atomic Energy Act of 1946.
Split into simpler sentences: Truman had touched upon one of the most sensitive issues in civil-military relations in the post-World War II period: civilian control of nuclear weapons. This was enshrined in the Atomic Energy Act of 1946.