Russia’s decision to end its mission to NATO seeks to undermine transatlantic unity and to deter the United States from pursuing additional escalatory measures. On Oct. 18, Russia announced it was ending its diplomatic mission to the Western defense alliance in Brussels and closing the NATO information office in Moscow after eight members of the Russian delegation were accused of being spies. While diplomatically significant, the move is unlikely to have a major impact on the extremely limited civil, political and military cooperation between Moscow and NATO following Russia’s annexation of Crimea in 2014. But it does risk straining relations within the bloc itself by driving wedges between the United States and its European partners on how to respond....