The armed uprising against Russia’s military command was called off just as quickly as it first began, but the fate of Yevgeny Prigozhin—the leader of the Wagner mercenary group who led the mutiny and incurred the enmity of Russian President Vladimir Putin—is now uncertain. On Saturday, Prigozhin reportedly agreed to leave Russia for an “early retirement” in Belarus after withdrawing his troops from marching on Moscow in a deal mediated by the neighboring country’s autocratic leader, Aleksandr Lukashenko, a close ally of Putin’s. “Realizing all the responsibility for the fact that Russian blood will be shed from one side, we...