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.

What explains the decline? A few things, including changing attitudes on war among leaders and voters, the spread of democracy (democracies don’t tend to fight with one another) and the role of United Nations peacekeeping. But one big, underappreciated reason for declining interstate war is that it doesn’t pay. Through most of history, global power and wealth have been determined by control of people, land and resources. Wars were fought over bodies and territory in zero-sum conflicts in which the victor took the spoils. Caesar was considered a Roman hero because he brought as many as 1 million slaves back from his Gallic wars alone. And as late as World War II, physical resources were still a key concern—Japan’s need for oil, Germany’s desire for Lebensraum (“living space”).

But power and wealth today are determined by technology, ideas and institutions. The World Bank estimates that nearly two thirds of global wealth is intangible—inventions such as the internal combustion engine or the solar panel that allow people to produce more power with less resources than older technologies, institutions including systems of property rights and education—leaving only around a third to be accounted for by built infrastructure, land and natural resources combined. Only in poorer countries are natural resources a large proportion of total wealth.

The richest, most powerful countries do not have the largest territory or population; they have the highest productivity. That is how California’s economy in 2018 is considerably larger than the world economy as a whole was in 1870. And the technological underpinnings of high productivity, such as the engines and solar panels and property rights, are “non-rival”—we don’t have to fight for them. If I occupy land, you cannot. If I use the technology of the internal combustion engine or double-entry bookkeeping, you can use it at the same time. In fact, if we both use the same technologies, we both benefit even more.

As a result, land and resources simply aren’t worth the cost of the fight for successful economies. And that helps to explain why the conflict that remains is increasingly concentrated in poorer countries where natural resources are still relatively important, especially in sub-Saharan Africa.

The low returns of war may also help to explain the limited military ambitions of China, which has the world’s second-largest defense budget—about 40 percent the size of America’s. While China clearly wants dominance in the South China Sea, the country has only two aircraft carriers—one of which is a secondhand boat left over from the days of the Soviet Union. It conducts bomber flights in international waters, but the two warships are limited to the same area. And it spends a smaller percentage of its gross domestic product on the military than does the United States: 1.9 percent compared with America’s 3.2 percent. China’s recent success has been built on global connections that have left it the world’s largest trading nation. A world war would tear apart those connections.

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.

This low efficacy of the Department of Defense is primarily because the military is limited in its ability to keep the peace in countries where much of the population doesn’t want it there at a cost in lives, finance and time that is acceptable to U.S. voters and lawmakers. And that is something repeatedly acknowledged by generals in the field in Afghanistan.

At the same time, the Defense Department is ill-equipped to deal with new international security concerns that are only going to grow. Rising productivity has increased carbon emissions and other pressures on global sustainability. Connectivity leaves people worldwide more exposed to threats from elsewhere including viruses real and virtual alongside financial contagion. These new national security challenges require a collective response: We can’t bomb our way out of climate change or financial crises—we have to cooperate through international organizations, agreements and the shared financial incentives for signing on to them.

The Pentagon’s failure to adapt is partially that it holds to the traditions of an institution designed to prevail on the battlefield; but the failure is also the result of massive waste. It is hard to exaggerate the scale of bureaucracy housed within the Pentagon. The total number of people working in the Department of Defense itself (none of whom are in the field actually defending or deterring war) climbed from 140,000 in 2002 to just shy of 200,000 in 2012. Nearly three-quarters of a million civilian federal employees work for the Defense Department—add in the Department of Veterans Affairs and that’s about half of the total civilian federal workforce. Again, none of these people are soldiers, sailors or airmen. The department also employed nearly 11,000 contractors to supply an additional workforce of over three-quarters of a million in 2010—although these are estimates, because the Pentagon does not know the exact figure.

They all support an institution that was recently declared simply unauditable due to complexity, failed systems and missing records—this after a $400 million effort involving over 1,200 auditors. (They’ll try again: The Air Force and Navy have issued $1.8 billion worth of contracts to help prepare for future auditing attempts). But from what we do know, there is an immense amount of waste. Retired Lieutenant General David Barno and colleagues from the Center for a New American Security have listed seven “deadly sins” of defense spending in a recent report, ranging from redundant overhead through inefficient procurement systems to excess infrastructure to a bloated retirement system that could generate annual savings of $49 billion if rectified. If that sounds too large to be plausible, in 2015, the Department of Defense itself reported administrative waste and excess bureaucracy cost the institution an annual $25 billion.

Under the circumstances, a federal bureaucratic system and budgeting process that dedicates more than half of all federal civilian employees along with one half of the federal discretionary budget to the Department of Defense is ripe for overhaul.

A budget cut to 1.5 times the military spending of our nearest competitor (China) would free up about $150 billion of the current $649 billion in U.S. spending (as reported by the World Bank). Taking $100 billion of that and adding it to the U.S. overseas development assistance budget would also bring the U.S. aid ratio up to 0.7 percent of gross national Income—the U.N. target.

In the longer term, over 10 years, the United States could move toward 2 percent of GDP going to defense, down from today’s 3.2 percent—that’s the target set for NATO as a whole back in 2006. And perhaps in 15 years, U.S. military spending could reach the current global median: 1.5 percent of GDP. At that point we could close down the Pentagon building, as it will have become too big for a slimmed-down bureaucracy overseeing a military at last focused on the violent threats of the future rather than the interstate conflicts of the past.

Each American citizen—man, woman and child—currently pays an average of $1,983 a year to the Department of Defense. Over an average lifetime, that adds up to $156,000 per person. It is a simply incredible sum for a country at zero risk of invasion and with a reasonable aversion to violent territorial expansion. Even Donald Trump wanted to buy Greenland rather than invade it. So in this presidential election cycle, candidates should get specific in their commitments to redeploy defense spending, and the numbers they use should be large.