My post on the possibility that recent tensions with the U.S. might lead America’s allies to conclude that they cannot ultimately rely on Uncle Sam’s nuclear umbrella and therefore decide to go nuclear themselves was written before seeing those now notorious Signal messages.

What was needed to avoid those allies taking that step, I had argued, was reassurance that they could rely on an American nuclear backstop.

It seems unlikely that Europeans will have found those messages reassuring.

More nuclear proliferation just came a touch closer.