The State Department is delaying the release of a volume from its U.S. foreign relations history that deals with the CIA-backed overthrow of an Iranian prime minister in the 1950s out of concern that publication could undermine nuclear diplomacy with the Islamic republic. The decision was made at a September meeting of the department’s advisory committee on historical diplomatic documentation and recorded in minutes released this week. The foreign relations records aren’t supposed to be suppressed for longer than three decades. Stephen Randolph, the department’s historian, informed the gathering that the volume on U.S. policy in Iran would be withheld...