"The U.S. military is currently sized to be able to conduct something less than two simultaneous or overlapping major conflicts," the Congressional Research Service noted in a report titled "Great Power Competition: Implications for Defense -- Issues for Congress," last updated in January.
For almost three decades after the end of the Cold War, the Pentagon maintained a "two-war construct," under which the U.S. made sure it had the ability to win two simultaneous wars in different theaters. The idea was that the U.S. would be able to take on a hostile country in the Middle East -- such as Iraq or Iran -- and still be able to defeat North Korea in East Asia.
But in 2018, a little-discussed, but fundamental shift took place in U.S. military planning.
Every four years, the U.S. Department of Defense issues its capstone military guidance called the National Defense Strategy, or NDS. Arguably, the most important element of the NDS is the "force planning construct," which specifies the number of conflicts the U.S. military should be prepared to face at the same time. That, in turn, determines the size of the defense budget.
In the 2018 NDS, the Pentagon adopted a "one-war" or "one-and-a half war" construct, shifting away from fighting multiple weaker enemies, such as terrorist groups or rogue states, to focusing all its energy on confronting a great power rival like China or Russia.
The unclassified summary of the 2018 NDS does not include an explicit statement about the force planning construct. But it does hint at the shift. The U.S. military will be capable of "defeating" aggression by a major power, while "deterring" opportunistic aggression elsewhere, the document said. This means that while the military is fighting its top priority war, the second front would be kept on hold until the first conflict was over.
Former Pentagon official Jim Mitre, one of the key authors of the 2018 NDS, confirmed that there was indeed a shift in mentality.
"This was a shift because it prioritized the ability of the U.S. military to defeat either China or Russia in one war above the ability to defeat two regional adversaries at the same time," he said in an interview.
Mitre, now a vice president and director of RAND Global and Emerging Risks, wrote in a 2019 paper that the "two-war" construct was outdated and potentially dangerous because it would result in a future force ill-suited to facing a great power rival.
But the realities of 2024 have muddled the game plan. Instead of focusing all attention on China, the U.S. is facing a potential four-front crisis: helping Ukraine push back a Russian invasion, supporting Israel in its stated goal to eliminate Hamas, handling an increasingly provocative North Korea, and preparing to halt a Chinese military operation to seize Taiwan.
Mitre told Nikkei that the danger is that the tradeoffs span across time frames -- the question being whether material support provided to Ukraine and Israel today is potentially undermining the ability of U.S. forces to respond to Chinese or North Korean aggression in the future.
A return to a two-war construct, as some analysts have called for, will be expensive.
"We should be contemplating a return to average Cold War-era levels of defense expenditure around 5 to 6% of GDP, which would be about $2 trillion in today's value," said Iskander Rehman, a fellow with the Kissinger Center for Global Affairs at Johns Hopkins University School of Advanced International Studies.
The fiscal 2024 U.S. defense budget is $842 billion, accounting for around 3.1% of gross domestic product. Forecasts have the ratio going down to 2.7% of GDP in 2032.
"Whatever way you look at it, we're entering an era when 2.7% of GDP is just no longer going to cut it," Rehman said.
Daniel Twining, president of the International Republican Institute, told Nikkei that the U.S. needs to spend "much more" on defense.
"The U.S. is never going to fight China and Russia at once. But the best way to deter China is to defeat [Russian President Vladimir] Putin in Ukraine. The best thing we could do in the Middle East is to see Israel vanquish terrorists who are sponsored by Iran," he said.
"Americans don't seem very strong these days at connecting the dots, but autocracies are working very closely together," and see the conflicts as connected, he said.
But Jennifer Kavanagh, a senior fellow in the American Statecraft Program at the Carnegie Endowment for International Peace, disagreed. "The financial cost of going back to a two-war construct would likely be unsustainable for the United States," she told Nikkei. "The war in Ukraine has shown how costly and intensive modern warfare can be, both in terms of the mass required and expense of high-end systems. Just preparing for and financing a U.S. war with China would strain U.S. resources."
And it is not only about money, Kavanagh added. "The military is facing a recruiting crisis, and it is not clear it could raise enough personnel to fight two wars at once without a draft, which is politically unpopular."
Sticking with the current concept of defeating one adversary while holding another off makes more sense, but the goal should be narrower, Kavanagh said. The U.S. does not have to "defeat" the Chinese military, but needs to adopt a strategy of denial that prevents China from achieving its key objectives, such as seizing Taiwan, she said.
While focusing on China, the U.S. should consolidate and draw down its forces in the Middle East and work to get regional partners to carry more of their own self-defense burden, Kavanagh said. "A lot of the challenges in the Middle East have diplomatic and economic, but not military, solutions."
Raphael Cohen, a senior political scientist at RAND Corp., has proposed a third way -- fight one war directly and another by proxy. He calls this the "Ukraine model."
The U.S. should size its military to win one war against one major power but size its defense industrial base to provide the wherewithal to win another by proxy, he wrote in War on the Rocks, a national security media platform, last January.
Who are those proxies? "Ukraine, and indirectly much of Europe, is fighting against Russia as we speak and to an extent, Israel is fighting a proxy war against Iran -- in both cases with American support, but no American troops," he told Nikkei. As for North Korea, "one would presume that South Korea would have a lead," he said.
Such a scenario would, in effect, mean that the U.S. is fighting to defend Taiwan, with which it has no treaty obligations, while leaving South Korea, a treaty ally, to fight for its own.
"A lot of this depends on how those wars break out, in what order, and how the policymakers at the time -- most notably the president but also Congress -- view these threats and American policy at the time," Cohen said.
"No matter the war, the United States would be looking to Japan for support," he said. "Japan is one of the United States' closest security allies and one of the cornerstones of security architecture in the Indo-Pacific."