 President Reagan and Vice President Bush were removed from participating in the exercise, however, it still remained one of the most realistic exercises to date, with a complete simulation of NATO forces going to DEFCON 1.The Soviet leadership's suspicion of Able Archer 83 as an attempt at a surprise nuclear attack masquerading as an exercise grew with intelligence collections of United States message traffic which was "unusual" in its message formats and communications procedures.The unusual message procedures led Soviet leadership to believe that Able Archer may not be an exercise at all.