The United States military recently began transitioning its training and operational practices away from the past two decades worth of anti-terror and counter-insurgency warfare, placing a larger emphasis on the resurgence of near-peer level threats posed by the likes of Russia and China. This sort of power competition is something the United States may be a bit rusty at, but it’s certainly not unfamiliar territory. The buildup of arms and military capabilities coupled with stern diplomacy and a side-eye toward national opponents is all part of the Cold War’s nuclear deterrent song and dance. If warfare between developed nations were still as simple as it was back during the hey-day of the Soviet Union, chances are that the U.S. would find itself back atop the heap through sheer power of budget… but modern warfare isn’t quite what it used to be, and that poses a problem for America’s longstanding warfare doctrines.

“In a western military campaign, we tend to shape the environment in Phase Zero, we deter in Phase 1, we seize the initiative in Phase 2, we dominate in Phase 3 combat operations, we stabilize in Phase 4, and we transition to civil authority in Phase 5,” Lt. Gen. Mark Kelly, Air Force deputy chief of staff for operations, explained to a crowd gathered at the Mitchell Institute in Arlington, Virginia, last week.

“The US is really, really good in the deter and win categories. But competition below the threshold of major combat ops is primarily where our strategic peer adversaries are executing their national and military strategies.”

Competition below that threshold of major combat operations has rapidly become the modus operandi of Russia and China, who both have leveraged their military strength in different regions of the world just enough to achieve their strategic goals without allowing their localized conflicts to spill over into actual warfare. Russia’s annexation of Crimea from Ukraine in 2014, as well as current tensions on the Russia/Ukraine border are an example of such an approach — as is China’s aggressive expansion throughout the South China Sea and even the joint strikes carried out by U.S., U.K., and French forces against sites in Syria tied to Bashar al Assad’s regime’s use of chemical weapons.

These military actions aren’t quite declarations of war, but rather seen as aggressive actions that could lead to war. International norms are shifting to allow for “punitive strikes” and even military annexations, provided diplomats and politicians are able to sell them to the public as isolated incidents — and that means trouble for the United States.

These “grey zone” conflicts that arise in places like the South China Sea and Ukraine place the U.S. in a difficult position as the sole remaining super power. Neither China nor Russia want to go to war with the U.S., but it’s important to note that the U.S. doesn’t want war with either of them either — and because no one wants a fight, tolerances are increasing to permit the aggressive pursuit of strategic ends without ushering in a third world war. The quagmire then becomes how to stop national level opponents from inching their way into more dominant positions by way of these “isolated” incidents.

The U.S. can’t solve its problems by declaring war, nor can it police the actions of near-peers in contested territory by force without prompting an economic fallout thanks to the world’s joint economy. War has never been simple, but in many ways, it has never been more complex.

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In order to succeed in the 21st century, America will need to acknowledge the disadvantage its economic and military superiority can sometimes be. Problems that could be solved by force can’t be without cascading effects throughout the world… and yet something has to be done when China or Russia commit egregious violations of the international norm. To date, America has employed the same strategy it always has — staring down its opponents and waiting for them to flinch.

But as recent incidents in the South China Sea have shown, America’s competitors know what’s at stake and are increasingly willing to call Uncle Sam’s bluff.

In an era of “grey zone competition,” the United States will need to find a way to compete… because war may be an outcome we all hope to prevent, but conflict is continuous.