But if we are not prepared to take these risks, then we must force the Ukrainians to abandon their deadly delusion. It would be up to us to prevent Russia from slaughtering Ukrainian conscripts in vain.

The only way to achieve this is for the West to oblige Ukraine to surrender. Ukraine is completely dependent on the International Monetary Fund, which is Western money. We must tell Kiev to accept as a fait accompli that Russia has carved out a South Ossetia in the east — or we turn the money off. We can console them: Being another Georgia is not the worst thing in the world.

We could save thousands of lives this way, but it would be a crushing defeat for the West. Russia would have restored itself as an empire — the former Soviet Union once more under the sway of the Kremlin. The West would thus concede, in effect, that Russia may invade or annex any of these territories as it pleases. And in these lands, the appeasers would flourish, and democracy wilt.

Russia would have triumphed over the world order imposed by the West after the Soviet Union lost the Cold War. This would mean the destruction of American geopolitical deterrence. America’s enemies, from China to Iran, would see this as an invitation to establish their own spheres of influence amid the wreckage.

Russia would not stop there. Mr. Putin wants to undermine NATO, and the smell of weakness would tempt him further. It would be merely a matter of time before Moscow exploited the Russians in the Baltic States to manufacture new “frozen conflicts.” Poland would feel compelled to act as though NATO did not exist, creating a defensive military alliance of its own with the Baltics; it might even establish a buffer zone in western Ukraine.

There is no easy way out now. But we must not let thousands of Ukrainians die because we dithered. We must be honest with them if we are not willing to fight a new Cold War with Russia over Ukrainians’ independence. But if we force Ukraine to surrender, rather than sacrifice lives in a fight for which we have no stomach, then we must accept that it is a surrender, too, for NATO, for Europe and liberal democracy, and for American global leadership. That is the choice before us.

Ben Judah is the author of “Fragile Empire: How Russia Fell In and Out of Love With Vladimir Putin.”