The Democratic National Convention’s final night included a stirring tribute to America’s veterans from a retired naval four-star admiral, complete with a backdrop of jets flying over a row of proud warships. But convention organizers may soon regret it. Norman Polmar, author of “The Naval Institute Guide to the Soviet Navy” and other military handbooks, told the Navy Times on Tuesday that the ships were Russian vessels. “The ships are definitely Russian,” Polmar told the military newspaper. “There’s no question of that in my mind.” The ships depicted in the Democrats’ backdrop had radar designs that the U.S. fleet doesn’t...