Which president made preventative war (which he called preemptive) the centerpiece of his foreign policy?

The correct answer is George W. Bush

It was a part of his Bush doctrine that revolved around Unilateralism and leading Preemptive wars. A preemptive war is the idea that if you know that someone is problematic, you should initiate a war and end that problem before it becomes a serious problem for the entire world. It was made after the 9/11 attack and revolved around preventing terrorism.