The war in Ukraine is getting more dangerous, in part because it is going better than Ukraine’s supporters could have imagined.

U.S. President Joe Biden has sought to reconcile two conflicting objectives: avoiding U.S. military intervention while also helping Ukraine and making Moscow pay a high price for aggression.

Yet as Russian President Vladimir Putin grows more desperate, that balance will become harder to strike. Potentially, the worse Russia does, the greater risks the U.S. and its European allies may face.