Complex sentence: This was one of the main causes that began the cold war, and perceived advantages of the adversary by both sides (such as the "missile gap" and "bomber gap") led to large spending on armaments and the stockpiling of vast nuclear arsenals.
Split into simpler sentences: This was one of the main causes that began the cold war. On both sides, perceived advantages of the adversary (such as the "missile gap") led to large spending on armaments and the stockpiling of vast nuclear arsenals.