The Department of Defense was created to win wars against nations that threatened the United States. That is still its major role: Of the Pentagon budget, 71 percent goes to research, development, testing, procurement, operation and maintenance, mostly of large weapons systems designed to defeat other countries’ military forces.

But interstate conflicts are going away. The last great power war began eight decades ago, and battlefield conflict has been on a declining trend since 1945. Battle deaths per 1 million people worldwide since World War II peaked at above 200 during the Korean War, reached about 100 at the height of the Vietnam War and plateaued at about 50 during the Cold War conflicts of the 1980s. In 2018, the number of deaths was around seven per 1 million people. Journalist Gregg Easterbrook reports that the last major naval engagement was in 1944, the last large air battle was in 1972 and the last major tank engagement was in the early 1990s…

Meanwhile, the United States retains a massive global military advantage, responsible for one out of every three dollars spent on defense worldwide and outspending the countries with the next seven biggest military budgets combined. But while that ensures dominance at confrontation on the battlefield, it is not so useful for the kind of conflicts the world still fights, dominated by guerrilla warfare. That is demonstrated by America’s not-winning streak over the past seven decades in civil conflict: Korea, Vietnam, Afghanistan and Iraq. The “Global War on Terror” drags on; the two countries suffering the most terror attacks in the world are also the two countries the United States has invaded in the past 20 years.