Yevgeny Prigozhin was, like Russian president Vladimir Putin, a street fighter in his youth in Leningrad in the former Soviet Union. He served nine years of a 13-year prison sentence for robbery, became a gangster and restaurant owner, government contractor, caterer to Putin, warlord, media mogul and propagandist. These days Prigozhin rules over the Wagner mercenary group that has earned a sinister reputation in Ukraine, Africa and the Middle East. Prigozhin’s mercenaries used the sledgehammer as a weapon of terror in Syria and Ukraine, so he turned it into their emblem. In January his television channel showed the heavyset, bald...