An American war against China or Russia would be truly awful. Even if the United States won — no sure thing — it could well suffer costs and casualties that would make the toll of the Iraq and Afghanistan wars seem minor by comparison. So is there a way the U.S. could stymie a Chinese attack in the Pacific, or a Russian land-grab in Eastern Europe, without having to defeat enemy forces head-on? This is the motivating question behind the idea of “horizontal escalation.”

Horizontal escalation is a strategic concept that relies on attacking an adversary’s weaknesses outside the theater where the fighting started, so as to avoid confronting its strengths within that theater. It is an alluring idea that has won support from some key national security professionals. Unfortunately, it probably won’t work.

Horizontal escalation is a response to a genuinely difficult problem: the immense challenges associated with directly defeating Chinese or Russian aggression.

As studies by the Rand Corp. have shown, if Beijing decides to use force against Taiwan, or Russia assaults its Baltic neighbors, the U.S. would be hard-pressed to respond effectively. American forces would be defending exposed territories on the adversary’s doorstep. They would have to project decisive power over thousands of kilometers, into areas where China and Russia can bring to bear formidable “anti-access/area denial” capabilities (sophisticated air defenses, anti-ship missiles and others). It would be harder than anything the U.S. military has done since World War II.

Suppressing enemy capabilities would bring additional dangers. Taking out Russian long-range artillery or neutralizing Chinese anti-ship missiles might require striking targets within Russian and Chinese territory. (In the Russian case, this dynamic is exacerbated by the fact that Kaliningrad, a part of Russia wedged between Lithuania and Poland, is full of advanced weapons and located behind NATO’s front lines.) These actions would raise the prospect of the adversary responding by threatening to use its nuclear weapons against U.S. or allied forces.

It is because these scenarios seem so ghastly that horizontal escalation looks so attractive. For years, U.S. strategists have argued that Washington should respond to Chinese aggression in the Western Pacific with a maritime blockade that would starve China of oil and other critical imports. Similarly, the U.S. and its allies could punish an aggressive Russia by leveling harsh financial sanctions, such as kicking Moscow out of the Swift global payments system. In theory, the U.S. military could even conduct operations in secondary theaters — targeting Russian forces in Syria, for example — as a way of distracting and punishing the enemy.

Rather than confronting China and Russia where the fighting would be toughest, the thinking goes, the U.S. would broaden the conflict into areas where it has the advantage, eventually inflicting enough pain that the enemy yields.

The theory of horizontal escalation thus holds that the U.S. can wage a war on its terms rather than the enemy’s — and that it can achieve victory without paying the price of a more direct approach. Unfortunately, this theory is too good to be true: Horizontal escalation ultimately stumbles on several key problems.

First, it underestimates the commitment of the adversary. Russia and China are governed by autocratic regimes that derive their legitimacy from a deliberate stoking of nationalism. Their rulers understand that it would be politically catastrophic — perhaps fatal — to start a conflict with the U.S. and then back down, particularly if their forces have not yet been defeated in the field. Once Moscow or Beijing decides to gamble by using force, in other words, they will presumably be willing to absorb a lot of punishment to avoid conceding defeat. This goes especially for conflicts where the object of aggression (Taiwan, for instance) is seen as a part of the adversary’s homeland, and recovering it is essential to the prestige of the ruling regime.

Financial sanctions or a far-seas blockade can inflict real pain, but probably not enough to persuade Chinese rulers to sign their own political death warrants. And both China and Russia are steadily working to make themselves less vulnerable to this sort of pressure: Russia by encouraging its oligarchs to bring their assets home so they are less vulnerable to Western sanctions, and China by building overland supply routes that are less vulnerable to American naval power.

Second, horizontal escalation suffers from a time problem. Coercion — particularly economic coercion — takes a while to work. But in the meantime, analysts such as former Trump administration Pentagon official Elbridge Colby have pointed out that the aggressor will be consolidating its gains and fortifying a position from which it cannot easily be dislodged. While the U.S. is waiting for coercion to have its effect, the situation on the ground — and at the negotiating table — will be steadily eroding. Meanwhile, America’s front-line allies such as the Baltic states will be left to absorb punishment or even occupation by Russian and Chinese forces — a possibility that will make them less likely to antagonize Moscow and Beijing by standing with the U.S.

Third, horizontal escalation is itself highly escalatory. A far-seas blockade of China would severely disrupt the international economy, beyond the shocks created by a localized conflict in the Western Pacific. And if the U.S. is obstructing oil shipments and interdicting third-party maritime traffic to China, then Washington may appear to be the one intensifying the war dangerously.

The U.S. might still find some forms of horizontal escalation useful in a major conflict with China or Russia, as a way of complementing rather than substituting for a more direct response. But its weaknesses as a standalone concept are such that for America to defend its interests in Europe and the Western Pacific it must be able to prevent Russia and China from conducting successful aggression in the first place.

As both the National Defense Strategy and the National Defense Strategy Commission have made clear, this will not be easy. It will require pushing allies and partners to develop their own anti-access/area denial capabilities, as opposed to the more expensive but less useful planes and large naval vessels that the Taiwanese, among others, seem to love. It will entail investing in new technologies that allow the U.S. to project power even in contested environments, and developing the new operational concepts that will enable American forces to use those capabilities most effectively. And it will involve making smart upgrades in America’s nuclear arsenal, to ensure that an adversary does not try to escalate itself out of conflict.

All these changes are only beginning, as some former Pentagon officials have acknowledged, and completing them will present a strenuous test of whether the U.S. can meet the challenges of deterrence and defense in the 21st century. But given the shortcomings of horizontal escalation, tackling those broader challenges squarely is still the best approach.

Hal Brands is a Bloomberg columnist and a professor at Johns Hopkins University’s School of Advanced International Studies.

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