Complex sentence: "Strength Through Peace" is a political theory designed as the counter to the Cold War era doctrine of "Peace through strength", which is the doctrine that military strength is a primary or necessary component of peace.
Split into simpler sentences: Strength Through Peace is a new doctrine designed to turn the Cold War era doctrine of "Peace through Strength"on its head. Under the Cold War thinking "Peace through strength" is the doctrine that military strength is a primary or necessary component of peace.