The battle of the billionaires has developed into a Cold War at Arsenal Football Club. E. Stanley Kroenke, a U.S. real-estate and sports mogul, and Russian oligarch Alisher Usmanov are the superpowers fighting for outright control of the Premier League team.

The latest flashpoint in their power struggle came Friday when Arsenal disclosed that after months of inactivity, Mr. Usmanov -- through his investment vehicle Red & White Holdings -- had acquired 668 shares in the North London club, increasing his stake to more than 26%.