Over time, the United States has become comfortable using greater levels of force abroad. This was not the case at the country’s inception: in the first eras of statehood, the United States engaged minimally outside North America, as many of its conflicts related to defending its borders, the frontier wars, and westward expansion. The United States’ involvement in World War I and World War II ushered Washington into global leadership and much greater global engagement. After the Cold War and especially following the 9/11 attacks, the percentage of armed disputes in which the United States was involved that were initiated by U.S. adversaries dropped precipitously. The United States now finds itself in an era in which militarily, its adversaries are provoking it less frequently—and yet Washington is intervening with armed force more than ever.

This is an unfortunate trend. For evidence, look no further than the disastrous U.S. military interventions in Afghanistan, Iraq, and Libya. The overly frequent resort to use of force also undermines U.S. legitimacy in the world. As the U.S. diplomatic corps and American influence abroad shrink, the country’s military footprint only grows. Global opinion polls show that more than half of the world’s population now views the United States as a threat. There could be a change in the offing, however: as China becomes a more potent power, the United States will be more likely to refrain from engaging in foreign interventions because it could end in a showdown with another superpower. And that ultimately could lead U.S. policymakers to pursue diplomatic and economic initiatives that could bolster the United States’ soft power and global credibility.

Rules of Warfare

To put the use of U.S. force into context, it is helpful to consider the conditions that would traditionally legitimate it. In contemporary international law, whose foundations date from ancient times, a legitimate resort to violence must satisfy three fundamental conditions. First, force can be used only in self-defense or the defense of an innocent bystander. Second, it must, whenever possible, represent a response in kind. If someone throws a rock at another person, it would be acceptable for the victim to throw a rock back but not to use a firearm (even though injury from both rocks and firearms can be lethal). Third, the violence must be proportional to that attempted or completed, wielded only to the degree needed to reestablish the peace. Given this, if a member of one group is injured by members of another, it would not be legitimate for the victimized group to kill one of the aggressors. These principles apply to interstate violence as well as to interpersonal violence. But a Latin aphorism captures a tragic misconception that shapes conflicts among states: Silent enim leges inter arma, “in wartime, the law is silent.” More commonly, this is understood to mean that when survival is at stake, anything goes.

But of course, not all conflicts are existential. It is arguably legitimate to believe that when a state’s survival is at stake, anything does go. But survival is rarely at stake—and it certainly is not at stake in the conflicts that Washington has started in recent decades. Although the cumulative impact of this U.S. propensity to resort to force may be invisible to U.S. citizens and their representatives, it is clear to U.S. adversaries and even allies abroad. A Pew Research Center poll conducted between 2013 and 2018 found that U.S. prestige has declined precipitously: in 2013, 25 percent of foreigners considered U.S. power and influence to be a major threat, a figure that rose to 45 percent five years later.

9/11 and Unipolar Inertia

Much of this change can be ascribed to the fact that in 2016, Donald Trump succeeded U.S. President Barack Obama. Trump’s snubbing of international norms and obligations to U.S. allies, his revocation of the Iran nuclear deal, his withdrawal from the Paris climate accord, and his aggressive outbursts against other countries on social media certainly encouraged these negative perceptions. But that is not the whole story. Several other factors help explain why the United States has become more prone to conduct military interventions and why global perceptions of American power have shifted as a consequence.

The first can be termed “the 9/11 effect”: a tendency to dehumanize adversaries. The jihadi embrace of suicide attacks on civilians convinced many Americans, including many policymakers, that the United States was facing an inhuman foe. In this view, the willingness of foreigners to die for a cause calls into question their rationality and, by extension, their humanity—even though the willingness to risk or sacrifice one’s life is considered heroic when undertaken in defense of the United States. In U.S. President George W. Bush’s 2002 State of the Union address, which he gave less than five months after the 9/11 attacks, Bush asserted, “Our enemies send other people’s children on missions of suicide and murder. They embrace tyranny and death as a cause and a creed.” Such states and their terrorist allies, Bush declared, “constitute an axis of evil, arming to threaten the peace of the world.” This habit of considering adversaries to be fundamentally different from other human beings or irrational helps explain the decline in the use of U.S. diplomatic and economic tools of statecraft in favor of a force-first foreign policy. Casting adversaries as a lethal force of nature, after all, makes bargaining or negotiating with them a fool’s errand.

A United States that does not wield all its military might would boost global perceptions of U.S. power.

Another explanation might be “unipolar inertia.” After the collapse of the Soviet Union and the Warsaw Pact in 1991, American commentators and analysts hailed the dawn of an era of unrivaled U.S. dominance, which the columnist Charles Krauthammer, writing in Foreign Affairs, termed “the unipolar moment.” This characterization was flawed because true unipolarity involves the capacity of a single state to defeat a combination of every other state in the system unaided. The United States did not have this power, so the immediate post–Cold War distribution of power is more accurately described as multipolar, with the United States in possession of a tremendous advantage in the power to win wars.

This asymmetry encouraged Washington to aggressively deploy its military around the world. And having internalized the habit of intervention abroad during the Cold War—supporting coups and assassinations, interfering in elections, conducting covert operations, and so on—in the name of national security, the sudden collapse of the only adversary that threatened its survival left the United States with an unrecognized dilemma.

It could have pulled back and demobilized in proportion to the new threat environment, which would have enhanced its legitimacy and reputation as a responsible global leader. But doing so would have meant standing idly by while long-simmering or emerging ethnic and civil disputes escalated to violence and, in Rwanda, Somalia, and the Balkans, descended into mass murder and genocide. Many American policymakers and analysts had come to believe that Washington’s Cold War interventions had aided the eventual U.S. victory over the Soviet Union. Old habits die hard, and as the self-proclaimed leader of the free world, the United States opted to continue intervening with military force—no longer to contain, roll back, and defeat Soviet communism but instead to protect human rights and advance democracy.

Drop the Sword

Another explanation for the trend of expanding U.S. intervention abroad is the fact that when the Soviet Union and the Warsaw Pact still existed, a force-first foreign policy may have been suppressed by the fear that escalating conflict could end in global thermonuclear war. The temporary suspension of great-power rivalry following the Soviet Union’s collapse and preceding China’s rise emboldened Washington to take more risks when it came to the use of force abroad.

But China’s growing military strength, enlarged economic power, and expanded global footprint should result in increased U.S. caution. That could herald a return to the U.S. tradition of diplomatic and economic statecraft as first resorts and armed force as a last resort.

This is true for three reasons. For one thing, although the United States has a legitimacy problem, China’s is even worse. Chinese President Xi Jinping has become a dictator and has committed China to a massive military buildup, all while aggressively intervening in the Indo-Pacific. China’s deliberate destruction of Hong Kong’s independence in 2020 and its escalating rhetoric—not to mention military exercises—against Taiwan have gravely damaged its international reputation. The best way the United States can take advantage of China’s growing legitimacy deficit is by reestablishing strong alliances in the region.

Second, a stronger China would place limits on the risks that the United States could take on the international stage without self-destructing. To be sure, there is a chance the United States could respond in a more assertive and interventionist way against a stronger China to preserve its global hegemonic position. But a more cautious foreign policy would be less likely to entangle Washington in new global conflicts, thereby protecting its own security and that of the international community.

Finally, a United States that does not wield all its military might would boost global perceptions of U.S. power. As the Russian Federation has found to its chagrin, unused power potential is a much better deterrent than military power exerted with grave human and economic costs. Washington would do well to reconsider using force abroad and refocus on diplomacy in the years ahead.

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