Trump’s lead envoy to Ukraine and Russia, Steve Witkoff, has had similar moments of confusion. In an interview in March, he could not name the regions over which the war is being fought. “These so-called four regions,” he said, struggling to recall them. “Donbas, Crimea... You know the names.”

Tragically, if he doesn’t, his most important foreign policy initiative will probably collapse — with violent aftershocks that could plague his entire term.

President Trump told European leaders that Russian President Vladimir Putin isn’t ready to end the Ukraine war because he thinks he is winning, according to three people familiar with the conversation...