On April 20, Vladimir Putin presided over the test launch of a nuclear-capacity intercontinental ballistic missile. The implications of the event, he warned, should cause Moscow’s enemies who represent outside threats to “think twice.” This, of course, is Putin’s latest use of the nuclear threat. At the beginning of the war against Ukraine, he warned of “the likes of which you [the United States and NATO] have never seen in history,” should Western aid to Ukrainian resistance emerge. On April 16, Putin issued a new warning of “unpredictable consequences,” following US President Joe Biden’s commitment of $800 million of military hardware to Ukraine, should the US and NATO continue to arm Ukraine. This threat followed on the heels of an announcement by Dmitry Medvedev, a senior member of Russia’s security council, that Russia will be forced to strengthen its nuclear forces in the Baltics should Finland and Sweden join NATO (which both have been deliberating).

These warnings constitute a pattern of the Kremlin’s nuclear sabre rattling that is aimed at deterring Western military assistance to Ukraine. Putin’s rhetoric is intended to communicate that there is no stopping him and that any such attempts will result in the unthinkable. How might the West (i.e., the US and other NATO members) respond? Most importantly, how should they respond? Can Putin be stopped by relatively free nations? And should he?

As a recent former White House national security advisor has observed in recent days, it is utterly unthinkable—indeed, doubly unthinkable—that a permanent member of the United Nations Security Council would resort to nuclear blackmail in its attempt to conquer another nation. Yet at the same time, the use of the inconceivable is wholly consistent with totalitarian regimes. Putin is committed to the war’s “escalation,” which is a euphemism for catastrophic and unspeakable slaughter. Ukraine’s valiant resistance against slaughter and tyranny thus far only increases Putin’s resolve to subjugate this people group and pour out his vindictive wrath.

As the war in Ukraine demonstrates, gone in our day is any semblance of world order and international security. Since the commencement of the war, Russian forces have perpetrated everything that international security institutions and declarations since the end of World War II were designed to prevent. In this light, it is incumbent on the West, with the US in leadership, to spell out to Moscow, difficult as this is for Western nations in general, that we will not tolerate the Russian campaign of slaughter and annihilation and that we will deter proportionately. We will not acquiesce to evil and permit Moscow to reassert Russian imperialism in a manner that resurrects the terror and horrors of Soviet tyranny.

Against the fears of many, both classical just war and Cold War thinking require that we retaliate not in kind or with a view of total destruction but proportionately to the threat. After all, this is the basic premise of “criminal justice”—in any context. Justice, which is non-fluid and universal in its character, requires a proportionate response, for the common good of all. One can only imagine the fear and chaos unleashed in our neighborhoods, communities, and cities if police and law-enforcement agencies were to throw up their hands in consternation and helplessness when and where confronted by the unleashing in our communities of injustice and horrendous evil at the hands of the lawless.

As The Economist rightly noted last weekend, if Russia wishes to impose its brutal vision on its neighbor, then that is “everybody’s business,” and not simply Ukraine’s. What exactly is at stake in Ukraine, after all? First of all, let us identify with 44 million people who call themselves Ukrainian. Remarkably, it is estimated that nearly 70 percent of the nation claims some sort of allegiance to the Christian faith; such numbers are almost unheard of in our world today. But the religious character of the Ukrainian population aside, the geopolitical significance of the unjust war being waged and raged against Ukraine is monumental and thus needs clarifying. This is a nation whose integrity, freedom, and sovereignty were affirmed by the US, United Kingdom, Russia, and Ukraine in the 1994 Budapest Memorandum. Where is the authority—and the moral backbone—to back and enforce this declaration by Western nations and Russia itself? Alas, it is non-existent. That is deeply troubling. Not only is this a moral abdication of our obligations to the community of nations and to Ukraine specifically, but it is also a denial of fundamental human rights. Moreover, it is tragic that in 2008 Germany and France blocked Ukraine’s accession to NATO; Putin, of course, has wasted little time in ensuring that Kyiv’s joining the alliance does not happen.

Not only at stake is the fate of almost 50 million innocent people whose integrity as a nation was promised, but a view of the world—a “worldview” and a world order—is at stake as well. In the vision of a revamped Russian empire—whose loss in 1989 Putin declared to be “the greatest geopolitical catastrophe of the twentieth century”—totalitarian tyranny, not an acknowledgment of basic human freedoms, becomes the norm. Thereby, not only is the West to be renounced, but smaller nations are to be subjugated, and without resistance. For Putin, then, the stakes in Ukraine are infinitely great. China, of course, is watching.

The West simply cannot continue hoping for any sort of “negotiated peace” in Ukraine; we have passed the point of no return. Putin has crossed the Rubicon, and the costs will be catastrophic and unspeakable. Putin’s goal, much like Joseph Stalin’s in the 1930s, is to eradicate the identity of the Ukrainians as a sovereign people and to ensure that Ukraine does not become part of any Western alliance, which itself through Russian eyes is a reminder of the Cold War debacle.

Off the battlefield, the West at the moment is losing the war of ideas and moral reasoning. We are so morally obtuse that we have difficulty distinguishing between a “just” and “unjust” war; even worse, we are reticent to defend those who are hopelessly caught in the demonic throes of an unjust war and genocide. As further evidence of this “losing battle,” just consider the demoralizing effect of the United Nations vote last week, in which 24 of 141 member nations voted not to remove Russia from the UN’s Human Rights Council and, more significantly, 58 of those 141 abstained from voting.

These stunning results only embolden the Russian dictator to do the unthinkable. But then we should not be surprised, given Putin’s formal agreement with Xi Jinping at the opening of the Winter Olympics in China in early February. In that agreement, the two dictators announced that there are “no limits” and that there is nothing “forbidden” in their fundamental and future unity. Both are committed to restructuring the post-Cold War geopolitical order. In Ukraine, the “forbidden” has been a recurring demonic pattern since the war’s beginning. And the recently appointed new commander of Russian forces, Gen. Alexander Dvornikov—labeled by some as the real “Butcher of Baghdad” based on his brutal efficiency in Crimea, Chechnya, and Syria—is surely an ominous sign.

Ukraine’s remarkably heroic resistance up to this point is absolutely galling and reprehensible to Putin. Tragically, however, Ukrainians’ bravery alone will not end the war. It will take nothing less than the West’s steel-willed military deterrence to prevent unspeakable slaughter in the days and weeks ahead. Putin’s periodic nuclear threats confirm this, as his latest attempt at blackmail indicates: the US and NATO members must back off.

What are the options before us? They are essentially two. Either we deter Russian aggression, which means that we convince Putin that we will not tolerate his first-strike nuclear threats and be intimidated, or we passively acquiesce to nuclear blackmail and Russian butchery of a nation that was promised its integrity and sovereignty five years after the Cold War ended.

What escapes many in our day is that the West, to a large extent, deterred nuclear war as a result of its Cold War policies. For decades, nuclear deterrence by the West, which was predicated not on first-strike capability but first-strike deterrence, was successful in averting war, not precipitating it. Those deterrents must be put in place now. The West’s response to Russia’s invasion of Ukraine, as Ukraine’s Defense Minister Aleksii Reznikov in recent days noted, has been too slow; the need is immediate. Time is running out. The aggressor needs irreversible punishment and deterrence. Russia has proven itself to be a terrorist state, and Putin will not stop. If Putin is successful in Ukraine, the result will be global chaos and confusion, in addition to unspeakable suffering and bloodshed in Ukraine that results in the annihilation and enslavement of a people group.

Can the West, with the US providing leadership, bring itself to ensuring Ukraine that her cause is just and winnable? Will we help defend Ukraine rather than simply make pronouncements from afar? Or will we shrink back—out of fear and intimidation—from a just response to cataclysmic evil, an evil that will set in motion unprecedented global chaos? The only strategy of preventing untold—and unspeakably tragic—suffering in the days ahead is to deter and prevent Putin militarily, so that Russian forces do not prolong mass suffering (which they will) and Putin does not employ nuclear blackmail (as he is doing and will continue to do).