On Jan. 1, Bulgaria became the eurozone’s 21st member when it gave up its 145-year-old currency, the lev, for the euro. In Sofia and Brussels, this development was roundly celebrated as another step in the European Union’s economic and political integration. What went largely unnoticed, however, is the extent to which Bulgaria’s adoption of the euro represents a strategic blow for the Kremlin. After years of sustained effort to block Sofia from joining the eurozone, Moscow failed to prevent a