Russia’s top security agency arrested an American reporter for the Wall Street Journal on espionage charges, the first time a U.S. correspondent was put behind bars on spying accusations since the Cold War. The newspaper denied the allegations against Evan Gershkovich. The Federal Security Service said Thursday that Gershkovich was detained in the Ural Mountains city of Yekaterinburg while allegedly trying to obtain classified information. The FSB, which is the top successor agency to the Soviet-era KGB, alleged that Gershkovich “was acting on the U.S. orders to collect information about the activities of one of the enterprises of the Russian...