In May 2017, an interviewer asked then-Secretary of Defense James Mattis what keeps him up at night. Today, amid Russia's invasion of Ukraine, increasing Chinese belligerence toward U.S. ally Taiwan, and the ongoing fallout from the loss of Afghanistan to the Taliban, some lawmakers and military experts question whether the Pentagon is projecting the kind of warfighting focus and ferocity that intimidate adversaries and deter aggression. This eroding confidence in the U.S. military largely stems from a belief that the Pentagon's senior leadership, both civilian and uniformed, is too focused on priorities other than deterring and preparing for war. One...