In his final public appearance as Russia’s defence minister on Thursday, Sergei Shoigu saluted Vladimir Putin atop Lenin’s mausoleum on Red Square, clad in a general’s uniform bedecked with medals. Andrei Belousov, appointed as his successor on Sunday, is cut from a different cloth. A Soviet-trained economist, Belousov has never served a day in the army and has served Putin, Russia’s president, in various roles as a civilian adviser on economics. Putin’s surprise tapping of Belousov to...