taboo has been broken in Europe. Only a few months ago, it would have been inconceivable for European leaders to propose sending European troops to Ukraine. But on February 26, French President Emmanuel Macron said the deployment of European forces to Ukraine could not be “ruled out.” Since then, other European officials have joined the chorus; the Finnish defense minister and Polish foreign minister have both suggested that their countries’ forces could end up in Ukraine. These comments, combined with existing support for such measures in the Baltic states, show that there is a growing bloc of countries open to...