When Russia invaded Ukraine on Feb. 24, it had hoped to overtake the country in a blitz lasting only days or a few weeks. Many Western analysts thought so, too. Three months later, however, Moscow appears to be bogged down in what increasingly looks like a war of attrition, with no end in sight and few successes on the battlefield. There was no quick victory for Russian President Vladimir Putin’s powerful forces that would allow the Kremlin to control most of Ukraine and establish a puppet…