Tension between Yevgeny Prigozhin, head of Russia's Wagner private militia group, and the nation's defense establishment exploded in dramatic fashion on Friday. The mercenary chief vowed to punish Russian military leaders, saying Defense Minister Sergei Shoigu had orchestrated a missile attack that killed "huge" numbers of his fighters. The Kremlin responded swiftly, denying the attack and accusing Prigozhin of mutiny. he internal conflict is the biggest test of President Vladimir Putin's authority since he sent troops into Ukraine 16 months ago.