When Redlines Fail

The Promise and Peril of Public Threats

With Russia massing troops on its border with Ukraine and apparently readying for an invasion, U.S. President Joe Biden’s administration has faced persistent questions about its redlines in that conflict. Senior U.S. officials have avoided spelling out exactly how much Russian aggression is too much, but they have stated clearly that a military invasion would trigger “massive” economic consequences for Moscow.

Washington faces similarly difficult questions about its redlines vis-à-vis other rising or revisionist powers. As the military balance of power between China and Taiwan shifts in China’s favor, some have called on the Biden administration to end the long-standing U.S. policy of strategic ambiguity and clearly commit to defending Taiwan in the event of a Chinese invasion. And in the Middle East, Iran is quietly getting closer to being able to build a nuclear weapon as hopes for a new deal with the United States hang in the balance, raising the question of whether Washington should draw a new redline on uranium enrichment.

In each of these cases, one potential downside of communicating well-defined limits to a U.S. adversary is clear: the adversary can simply ignore them, forcing the United States to follow through on its threats or else look weak and unreliable. Critics of redlines often cite President Barack Obama’s failure to enforce his redline against President Bashar al-Assad’s use of chemical weapons in Syria as an example of why the tactic is bad policy. The episode dented the Obama administration’s credibility, they argue; some have even gone as far as arguing that it emboldened Russia to invade Ukraine in 2014. Retired General Jim Jones, who served as Obama’s first national security adviser, later characterized the Syria redline as a “colossal mistake.”

But potential embarrassment is not the only—or even the most important—problem. Redlines are often self-defeating for strategic and psychological reasons: public threats can provoke targets to resist or retaliate instead of backing down. Furthermore, overly aggressive threats in defense of redlines can reduce the incentive for U.S. adversaries to comply; the targets of redlines must believe that conceding will produce better outcomes than resisting. Washington too often undermines assurances of this type by overselling its threats, convincing adversaries that they will reap no reward from heeding its redlines.

Yet abandoning redlines altogether is not the answer. Washington cannot simply sit back and wait for hostile countries to behave in ways that harm U.S. interests. Rather, U.S. policymakers must understand that assurances matter as much as threats and that carefully calibrated redlines are almost always better than strident, dogmatic, and bluntly worded ones.


Redlines—and threats more generally—fail more often than they succeed. Economic sanctions, nuclear threats, bombing campaigns, and cyberattacks rarely convince countries to capitulate. Countries hardly ever acquire territory via threats. And even the strongest states find it difficult to coerce weaker adversaries, a problem that is all too familiar to Washington.

The United States struggles to use redlines effectively in part because it often has less at stake than its adversaries. Moscow cares more about Ukraine than Washington does. China values Taiwan more than the United States ever will. Such asymmetry in interests partly explains why leaders often struggle to make their redlines credible.

To overcome this disadvantage, leaders sometimes pursue credibility by making threats in crystal clear language or announcing them in high-profile settings. But doing so puts leaders in a bind. If the redline fails, they must choose between two bad outcomes: back down publicly or risk being drawn into a cycle of escalation—perhaps even into an unwanted war.

Redlines—and threats more generally—fail more often than they succeed.
It is for this reason that critics of redlines most often argue that they risk damaging a country’s global reputation. On balance, however, concerns about widespread reputational costs from backing down are overblown. As the political scientist Daryl Press has argued, leaders assess the credibility of their adversaries not by their past actions but by their present interests in a given crisis. For this reason, most leaders of NATO countries perceive Russia’s threat to invade Ukraine as credible even though Russia has mobilized troops along the Ukrainian border before without invading. Similarly, during the Cold War, the United States took seriously Soviet Premier Nikita Khrushchev’s 1961 ultimatum on the status of West Berlin even though he had backed down from a similar ultimatum in 1958. It is difficult to think of a country that backed down from a redline and was therefore unable to make credible threats.

Rather than damaging a state’s overall reputation, decisions to back away from redlines provide information about a state’s specific interests. Biden’s withdrawal from Afghanistan revealed that he was unwilling to remain in the country indefinitely to prevent a Taliban takeover, but it said little about whether he or his successors would fight to defend Taiwan if China invaded the island. Obama’s decision not to attack the Assad regime after it violated his redline in 2013 similarly revealed something about his willingness to punish the use of chemical weapons, but it is farfetched to blame this decision for Russia’s 2014 invasion of Ukraine. A few airstrikes in Syria would not have changed Russian President Vladimir Putin’s calculus.


But even though redlines pose less of a reputational risk than is widely believed, they pose more of another kind of risk. Redlines don’t merely threaten—they provoke.

Confronted with public threats, leaders immediately gain new reasons to do the opposite of what their adversaries demand. It is not just those issuing redlines who risk embarrassment from not following through. The targets of such policies have at least as much at stake, and they prefer not to look weak by capitulating. Indeed, targets sometimes retaliate against redlines, including by setting redlines of their own. When Putin demanded that NATO commit to excluding Ukraine from joining the alliance, Biden responded by threatening Putin with sanctions “like none he’s ever seen.” Washington should not be surprised when its redlines provoke similar reactions.

Redlines elicit psychological responses from their targets that undermine their own chances of success. Leaders, like other people, value their autonomy. They bristle at manipulation and coercion. One way to preserve a sense of autonomy is to do exactly what has been prohibited. It is no surprise that when leaders are backed into a corner by foreign demands, they often fail to dispassionately weigh the costs and benefits of complying. Anger and indignation are normal human responses to unwelcome coercion.

Redlines don’t merely threaten—they provoke.
Consider what happens every time China reasserts its expansive claims to the South China Sea—which, if accepted by Washington, would prohibit U.S. warships from operating in what the United States and the rest of the world regard as international waters. Far from complying, the United States responds with new freedom-of-navigation operations in the area. Washington must understand that its redlines have the same effect on Beijing. Every time it sends warships through the South China Sea or sells arms to Taiwan, China responds with its own demonstrations of power and authority. Even aggressive U.S. rhetoric meant to deter Chinese violations of Taiwanese airspace might in fact be prompting more violations rather than fewer. For strategic and psychological reasons, redlines tend to provoke the very actions that they seek to deter.


But even redlines that are credible and do not provoke their targets sometimes fail to achieve their intended result. Consider, for example, that Putin has convinced the leaders of NATO countries that he is willing and able to invade Ukraine, but he has nevertheless failed to obtain the commitment that he seeks from the alliance to halt its eastward expansion. Russia’s core problem is not issuing credible threats but rather making credible assurances. If NATO leaders agreed to take Ukrainian membership off the table, they could not be sure that Russia would not use similar threats in the future to make new demands. Successful redlines must come with credible promises that complying will not result in costs being imposed anyway—or in greater demands in the future.

U.S. policymakers would be wise to consider this as they craft their own redlines to constrain Russia. Imposing sanctions on Moscow before it attacks Ukraine would be a mistake. Washington should instead create the strongest possible incentive for Putin to stand down by making clear that U.S. sanctions will be maximized if Russia invades and minimized if it does not. Biden has all but ruled out a U.S. military intervention in Ukraine, but threatening sanctions is futile if the Kremlin expects them regardless of what it does.

The lack of credible assurances poses an even greater impediment to restoring the 2015 nuclear deal with Iran or reaching a new one. U.S. President Donald Trump’s decision to withdraw from the 2015 accord and impose sanctions on Iran even though the Islamic Republic had complied with the terms of the deal has understandably eroded Tehran’s faith in American promises, prompting it to make the impractical demand that Biden bind his successors to any new deal.

If Iran’s experience after complying with American redlines was bad, other countries that have made nonproliferation bargains with Washington—ostensibly the success stories of nonproliferation redlines—have fared even worse. After the Gulf War, Saddam Hussein agreed to give up Iraq’s weapons of mass destruction, including its nuclear program, in exchange for peace. He kept his end of the deal. But 12 years later, the United States invaded Iraq under false claims that Saddam still had such weapons. In 2003, the Libyan dictator Muammar al-Qaddafi relinquished Libya’s nuclear program in exchange for promises of progress toward normalized relations with the United States. He, too, abided by the deal. Eight years later, the United States joined a NATO mission that overthrew Qaddafi and led directly to his brutal death. Most telling of all, Ukraine returned to Russia the nuclear weapons it had inherited when the Soviet Union collapsed as part of a 1994 agreement that committed Moscow to “refrain from the threat or use of force against the territorial integrity or political independence of Ukraine.” Russia has not kept that promise.

Offering credible assurances is surprisingly difficult. Doing so often requires easing pressure on a bitter adversary. A new deal with Iran would require a credible promise of sanctions relief, but critics of this diplomatic approach prefer to use sanctions to weaken the Iranian regime instead of as leverage to prevent nuclear proliferation. One reason it is hard to make assurances credible is that the same policies that increase the credibility of threats often undermine the credibility of assurances. The United States can demonstrate its readiness to enforce a redline by convincing Tehran that it is willing to impose the harshest possible sanctions or by imposing additional sanctions now. But that approach could make it harder to lift sanctions once a deal is made, heightening Tehran’s fears that it will face sanctions no matter what it does. In other words, threatening the strongest possible sanctions against Iran may strengthen U.S. redlines, but even the most credible threats won’t matter if Iran believes that Washington is determined to impose (or retain) sanctions regardless of what concessions Tehran makes.

In the end, setting redlines is neither wisdom nor folly. Given the lack of appealing alternatives, Washington will inevitably need to use this tactic to bargain with and deter adversaries. But it need not do so under false assumptions. The reputational risk of walking back from a redline is not as great as many fear. Nor are the strongest redlines—or those that are trumpeted with brash language and swagger—the most effective. Such threats risk provoking more than they coerce and establishing credibility at the price of assurance. To be effective, redlines should be carefully calibrated to convey U.S. demands, provide necessary assurances, and avoid provoking their targets. Whether the United States is dealing with China, Iran, or Russia, striking the right balance will be the key to success.

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