Can the U.S. afford a major war? Not with this deficit.

Warning: This graphic requires JavaScript. for the best experience. (Kyle Ellingson/For The Washington Post) Opinion Editorial Board Can the U.S. afford a major war? Not with this deficit. The enemy gets a vote in foreign affairs, and nobody knows what the 2030s will hold. Will China invade Taiwan? Will NATO allies need defending against Russia? Will terrorism in the Middle East or Africa require a response from the United States? Will another emerging threat demand American action? The federal budget is not prepared for such contingencies. Judging by the size of the deficit alone, one might assume the U.S. is already fighting a war far more involved than the on-again, off-again bombing of Iran. The additional burden of borrowing to finance a full-scale, protracted conflict could push the budget into more dangerous territory than it already is. 'The most significant threat to our national security is our debt,' said then-Chairman of the Joint Chiefs of Staff Michael Mullen — in 2010, when the national debt was about $27 trillion lower than it is today. National security is the primary purpose of the federal government. For much of American history, defense accounted for the bulk of federal spending. It was possible to identify wars just by looking at peaks in the debt-to-GDP ratio. Then, when the war was over, the ratio came back down as the need for taking on debt receded. That's no longer the case because non-defense spending has overwhelmed defense. Winning World War II was expensive, and in 1945, national defense spending made up 90 percent of federal outlays. During the Vietnam War, the level was between 35 percent and 50 percent. By 1999, after the Cold War ended and the peace dividend came, the portion for defense had dropped to 16 percent. Even the wars in Afghanistan and Iraq after the terror attacks of Sept. 11, 2001, barely pushed defense over 20 percent of federal spending. This year, defense accounts for 13 percent of federal outlays. The Congressional Budget Office projects that by 2035, it will fall to single digits. Beginning in 2032, more than half of all federal spending will go toward just Social Security and major health care programs. Of course, the U.S. still spends a lot on defense, over $900 billion this year. One reason America's defense budget is so much higher than other countries' is that the U.S. is a high-wage country with an all-volunteer force. Rather than forcing people to serve, the military has to compete with private employers for workers. Eliminating the draft has been good for personal freedom, and the military is hitting its recruiting targets just fine. But relying on volunteers rather than conscripts means that paying troops must be a major part of the military budget, and cutting benefits makes the Defense Department a less attractive employer. About 4 in 10 dollars of the Pentagon's budget go to compensate military personnel or civilian employees. The only employer in the world larger than the U.S. military is the Indian military, and compensation costs for the U.S. military are nearly four times greater than India's entire defense budget. Military pay raises are linked by law to average private-sector pay raises, meaning the Pentagon's payroll costs grow at roughly the same rate as the overall economy's. Because of years of delay on defense modernization efforts, the U.S. needs to rejuvenate its conventional forces and nuclear deterrent simultaneously. All three legs of the nuclear triad (bombers, submarines and land-based missiles) rely on decades-old technology. The Iran conflict has shown that the Army, Navy and Air Force are all stretched thin. Modernization efforts are already partially underway, and they will extend into the 2030s and beyond. Then, there are the unknown needs of the future. Drone warfare, based on the experience of Ukraine, requires much nimbler procurement systems, as technology can become obsolete in months rather than decades. Each unit of unmanned technology is cheap, but costs accumulate due to the enormous quantity of drones required and their quick depletion. Drones are not replacing more expensive conventional weapons, at least not right away, so they'll be an added cost in the 2030s. They won't supplant existing spending. There is plenty the Pentagon can do to be more efficient. It's a government bureaucracy like any other, prone to bloat as bureaucrats measure their success by the size of their budgets. The inherently uncompetitive defense market, where one customer deals with a handful of contractors, isn't conducive to cost effectiveness. But defense spending is not driving the national debt. The CBO projects that the defense budget will grow slower than the economy over the next decade, meaning it will pull the projected total debt-to-GDP ratio down. Of course, those are baseline projections that assume no wars happen and don't include proposals such as President Donald Trump's desired $1.5 trillion annual defense budget. For perspective, the $13 billion price tag on a Gerald R. Ford-class aircraft carrier equals about three days of Social Security spending. All purchases of guns up to 30mm caliber across all military branches in 2025 cost about $650 million, less than four hours of Social Security spending. The projected all-in cost of buying, operating, maintaining, upgrading and fueling the notoriously expensive F-35 program over its entire 94-year lifecycle is less than last year's spending of $2.3 trillion on Medicaid and Social Security. Defending the country is Washington's most fundamental responsibility. Governments are expected to take on debt in wartime and pay it down in peacetime. Stretching the market for government debt to the limit in peacetime is a dereliction of duty and, ultimately, a danger to national defense.