Negotiation between the US and Russia has failed. Putin demands that NATO make major concessions or he will attack.

Putin would be more likely to forego war if Ukraine were more strongly defended. The US should have made sure to strengthen Ukraine enough to deter war; there was no danger in doing that.

Threatening sanctions never had much chance of success. Indeed, sanctions have usually failed to change other countries' foreign policy. They often hurt the people of the targeted country, but its dictator generally doesn't care about them.

The sanction that would worry Putin is to refuse to buy Russia's gas, but Europe hasn't got the courage to do it. Indeed, Russia is cutting its gas sales to Europe to provoke distress there and make European leaders timid. The courageous response for Europe would be to boost construction of renewable generation facilities, while meanwhile using temporary measures to help people get along with less gas.

It would have been wiser all along for the US not to try to extend NATO to Ukraine and Georgia. But the way Putin has shaped this confrontation, to agree to the demand now would be an abject surrender.