The collapse of the Cold War–era nuclear arms treaty signals trouble for U.S.-Russia relations, European security, and nonproliferation efforts.

The first summit between Joe Biden and Vladimir Putin eased some of the tension in the fraught U.S.-Russia relationship. It also laid bare the difficult path ahead to resolving differences on many is…

President Biden’s goal of bolstering democracies around the world will need robust U.S.-Europe cooperation to succeed.