Deterrence Collapsed When Putin Invaded Ukraine. Have We Learned Our Lesson?

This week marked the fourth anniversary of Russia's full-scale invasion of Ukraine – with peace as elusive as ever.

I was in Ukraine for this somber occasion and was once again impressed by the resilience and fortitude of this incredible country. Each night I was there, air alert sirens sounded and ballistic missiles and drones reached Kyiv consistently. This is a fact of life for the Ukrainian people – yet they remain unbowed and unbroken. Cities continue to function, and necessity has driven innovation across multiple sectors necessary to keep the country running.

Like all decent human beings, the Ukrainian people are tired of war and want peace – but not at the price of their sovereignty. Let's be perfectly clear: The responsibility for the war's continuation rests entirely with Vladimir Putin. Ukraine has continued to fight valiantly, while also showing its willingness to make painful concessions to bring the war to an end. However, President Volodymyr Zelenskyy's government draws the line – quite rightly – at ceding highly strategic territory in the Donbas region that Russia has not managed to capture.

Putin has toyed with the Western interlocutors eager to broker a deal, while showing zero willingness to make any real compromises. He is willing to inflict limitless suffering on the people of Ukraine to try to break their spirit. What's more, he has no regard for the lives of his own soldiers, whom he treats as mere cannon fodder.

If we let him get his way, it will only be a matter of time before he is able to complete his conquest of Ukraine, a victory that will only whet his appetite for further gains. This would be a disaster not only for Ukraine but for global security writ large.

On that terrible day four years ago when Russian troops began their assault on this sovereign nation, the world witnessed the total collapse of deterrence. Emboldened by the Biden Administration's weakness and fecklessness – qualities on full display in the botched withdrawal from Afghanistan – Putin made a gamble that he could launch this blatant war of aggression and get away with it.

But Ukrainians were made of sterner stuff – and their bravery shook the West out of its stupor. NATO was reinvigorated and galvanized to make good on promised increases in defense spending (commitments made thanks to our efforts under the first Trump Administration). Ukraine received the military and diplomatic backing it needed to fight back, and the easy victory that Putin had clearly expected never materialized. Instead, Russia has suffered humiliating losses of blood and treasure at the hands of a much smaller power, sustaining an estimated 1.2 million casualties, massive losses to its military infrastructure, and severe damage to the economy.

While Ukraine may have received the support it needed to stay in the fight, it was never equipped with what it needed to win. This gave Putin time to recover from his losses and dig in his heels, making the reasonable calculation that the West would eventually abandon Ukraine.

Opponents of support for Ukraine claim that providing it with the kind of military support necessary to truly turn the tide against Russia often argue that doing so will risk setting off World War III. In fact, it's the failure to act decisively to put Putin in his place that poses the greatest danger.

Tyrants only respond to strength, and Putin will only stop his brutal war if the costs of continuing are too high to bear. Increasing pressure on the aggressor is the only way to secure an outcome that restores Ukraine's sovereignty, safeguards European security, and deters bad actors from future belligerence. In contrast, it is the perception of weakness that is provocative. Make no mistake: Xi Jinping of communist China is watching very carefully as he plots to make his move on Taiwan. If that happens, we could truly be at the threshold of World War III.

If the United States is serious about securing a peaceful outcome, appeasing Putin is the last thing we should be doing. President Trump has told President Zelenskyy that he wants to see a settlement by the end of June 2026. Working with our European partners, America should ratchet up the pressure for Putin to come to the table by providing Ukraine with the materiel it needs to strike deep into Russian territory, while hammering down the terms of a binding security commitment with multiple layers of verification and enforcement to guarantee Ukraine's sovereignty.

Thanks to President Trump's decisive exercise of American power, the U.S. has made great strides in rebuilding the deterrence lost under Joe Biden's presidency. But those achievements could all be for nought if we don't get this critical piece of the geopolitical puzzle right.