As Poland observes a day of remembrance for the victims of a Ukrainian nationalist military unit, there are increasing signs that it could cut off its neighbor from military aid, even as the war against Russia continues.

Poland, steeped in bad memories of the 1939 invasion and decades of Soviet dominance after World War II, is a firm backer of Ukraine’s defense against Russia. But a flare-up over…

As Poland observes a day of remembrance for the victims of a Ukrainian nationalist military unit, there are increasing signs that it could cut off its neighbor from military aid,…