There is a problem with deterrence; it’s not working. Not that we are about to descend into nuclear armageddon. But aside from nuclear wars, the United States’ deterrence paradigm does not seem to be deterring much recently. Our adversaries—principally Russia and China—do not seem cowed, either by the risk of failure to achieve their objectives or by the fear of retaliation. Both have been seizing the initiative with aggressive behavior ranging from information warfare, through the full range of gray zone tactics, all the way to the illegal military invasion and occupation of a sovereign neighboring state. Either the theory of deterrence is wrong, or the West is doing deterrence wrong.

The litany of Russian aggression in recent years includes the massive 2007 cyber-attack against NATO ally Estonia, the 2008 Russian seizure of the Georgian provinces of South Ossetia and Abkhazia (15 percent of Georgia’s territory), the 2014 occupation and illegal annexation of Crimea, and the 2015 intervention in Syria. Russia’s actions in Crimea sent shockwaves through the West, yet Russia’s main objectives, attained through well-planned cross-domain operations, were achieved at little real cost. In February 2022, confident in his impunity despite threats and warnings from Western powers, Russian president Vladimir Putin launched a full-fledged aggressive war against Ukraine. At the time of this writing, the war still rages in that beleaguered country as the death toll approaches half million.

Meanwhile, China—dubbed our so-called pacing threat—has been relentlessly and unapologetically stealing Western intellectual property for years at next to no cost in what was described by former National Security Agency director Keith Alexander as “the greatest transfer of wealth in history.” China has militarized the South China Sea, weaponized atolls in disputed waters, and bullied, threatened, and coerced neighbors and extra-regional countries that have dared to defy its strategic demands. The brutal repression of the Uyghurs and the brazen abrogation of the Hong Kong agreement and guarantees were met with loud protests from the West as well as limited economic sanctions, but nothing sufficient to deter China’s aggression.

Real deterrence depends on our will and our capability to inflict unacceptable costs on an adversary. If our adversaries believe that our intervention will prevent them from achieving their objectives, or that they will suffer unacceptable retaliation and consequences, they will be deterred. But deterrence requires credibility, and that is where the West in general, and the United States in particular, come up short. Who can forget President Barack Obama’s red line warning to Syrian president Bashar al-Assad in August 2012 against the use of chemical weapons? Clearly, Russia and China haven’t. President Joe Biden took the military option for defending Ukraine off the table and has refused Ukraine permission to use U.S. weapons for retaliatory strikes on Russian territory. Our failure to demonstrate both the will and the capability to retaliate that undergird deterrence undermines deterrence.

Our fear of escalating the conflict in Ukraine has created an atmosphere of self-deterrence. We fear that any retaliatory action will exacerbate the situation and unleash an escalatory upward spiral, perhaps approaching or even crossing the nuclear threshold. While understandable, this mindset acts powerfully to restrain any credible demonstration of our capability and will. Meanwhile, our adversaries continue their persistent, multi-domain campaign against U.S. and Western security interests capitalizing, as they see it, on our paralysis. As the devastation of Ukraine drags on as China’s Xi Jinping, North Korea’s Kim Jung-un, and the Ayatollahs of Iran watch carefully and study. Indeed, Ukrainian cities are now routinely attacked by Iranian drones, sold to and deployed by the Russians. And soon, if not already, Ukrainian cities and troops will be bombarded by North Korean artillery shells traded to the Russians for food, by Kim. Neither of these odious regimes are deterred from actively, perhaps even enthusiastically, participating in the destruction of Ukraine and the murder of its people.

The lack of credibility has emboldened our adversaries who will inevitably push against and probe our environment of self-restraint, seeking to measure and understand where America’s will to act matches the need to defend its vital interests. For the moment, our adversaries believe our will to act is not aligned with our interests. As such, the persistent probing continues across a wide frontage and across multiple domains, especially in the cyber domain. Using an old metaphor, our enemies are pushing in the pin—globally—and carefully measuring when, where, and how they will strike an American nerve, and then how the United States will react. Understanding and anticipating the U.S. reaction will form the basis for their challenges against the U.S. and our allies. The lower the American threshold for either symmetrical or asymmetrical reaction to these now nearly constant probes, the greater the credibility of our deterrent. Conversely, the higher the threshold of American reaction, the more emboldened our adversaries become and the more risk we must absorb.

The Russian war in Ukraine exemplifies this situation clearly. Our fear of escalation has kept the West from taking the steps necessary to end the war. Putin has shown us he will not be deterred by economic sanctions. By now we should have learned that economic sanctions—regardless of how good they may make us feel, or even despite the harm they may cause to our adversaries—do not deter a determined foe. Cuba, North Korea, Iran, Venezuela, as well as Russia and China, have been resistant to, and in some cases completely undeterred by, economic sanctions. If Putin is willing to sacrifice 200,000 soldiers, he is unlikely to be deterred by lower gas and oil revenues. By contrast, consider how effectively Putin has used the specter of nuclear escalation to deter an effective counter-offensive in Ukraine by nuclear saber-rattling. The debates about providing Ukraine with tanks; long-range, precision-guided missiles, F-16s, and other weapons, have been heavily influenced, and sadly, lengthened, by a strong sense of self-deterrence.

Western fixation on preventing escalation is compounded by an anachronistic interpretation of the laws of armed conflict which require any retaliatory operation to be proportional to the provocation, militarily necessary, and limited to military targets. These principles make sense in the context of conventional warfare, but contemporary conflict has metastasized far beyond the conventional sphere and now includes never-ending sub-threshold attacks, probes, and all the ambiguity of the so-called gray zone. These aggressions frequently defy rapid and unequivocal attribution and are often perpetrated by non-military agents.

It is noteworthy that the Western binary notion of war and peace is not shared by our principal adversaries. Both Russia and China perceive international relations as a constant and permanent struggle to create “positional” advantage to achieve strategic objectives that are in direct conflict with our values and interests. Given the persistent multidimensional threats we face, to which specific act of aggression would or should we respond? How can we determine if the act was perpetrated by a military or a non-military agent? Was it government-sanctioned, or just government-tolerated? This ambiguity converts the principles of military necessity, distinction, and proportionality into competitive handcuffs.

These observations beg the question: can there be any comprehensive theory of deterrence in the twenty-first century with so many incongruities and discontinuities? What does deterrence look like when dealing with a nuclear-armed opponent? What deters Al Qaeda, ISIS, or transnational criminal networks? What about cyber deterrence, and the real likelihood that we’ll soon encounter AI-powered, lethal autonomous systems? What deters attacks on our orbital constellation and our undersea fiber optic cabling by any entity capable of disrupting or disabling them? Witness the confusion over the damage to Nordstream II. Is there a single, master, comprehensive deterrent narrative that can simultaneously and concurrently work for us across all these domains and against all these state and non-state actors?

What is clear is that the base truism of deterrence theory remains the same: for deterrence to work in any domain our adversaries must believe we have both the will and the capability to prevent them from achieving their objectives or risking unacceptable pain. The re-building of Western defense forces over the past decade has been dramatic, but regrettably has also been frequently mitigated by strategic paralysis and equivocation. Declaring we have the will or declaring red lines will not suffice, and have already shown themselves to be inadequate. Words must be matched by deeds and actions. For Russia or China to believe in our deterrent we must break the cycle of reacting to their provocations and be prepared to be resolute in our intention to inflict some real pain in retaliation. This entails risk, but without taking some risk there will be no change in our adversaries’ behavior, and the persistent probes for our weak spots and the attacks on our vulnerabilities will be never-ending. Every strategic act entails some risk but so does no action. And no action, we know, is no deterrent at all.

General John R. Allen (USMC ret.) is a former President of the Brookings Institution, Special Presidential Envoy for the Global Coalition to Counter ISIL, and Commander of ISAF.

Michael Miklaucic is a Senior Fellow at National Defense University and the Editor-in-Chief of PRISM.