The intense reaction Tuesday night to news of a Russian-made missile striking a NATO ally, Poland, since understood to be a false alarm, was a sobering reminder — if one were needed — of the risks that an already brutal conflict in Ukraine could escalate into a wider war that brings Russia and NATO into military confrontation.

There are essentially two concerns. One is that a long, bitter war with forces battling on the ground, and missiles and shells flying through the air, will create accidents and incidents that can become something bigger — for instance, if it were clear that Russia had hit a NATO country, even if by accident, as was the initial fear Tuesday night.

The second and probably more dangerous prospect is that Russia might calculate that the use of nuclear weapons would provide it some advantage, either militarily or politically, to divide the trans-Atlantic alliance and cause civilian panic.