Because Able Archer 83 simulated an actual release, it is likely that the service and technical personnel mentioned in the memo were active in the exercise. More conspicuously, British Prime Minister Margaret Thatcher and West German Chancellor Helmut Kohl participated (though not concurrently) in the nuclear drill. United States President Reagan, Vice President George H. W. Bush, and Secretary of Defense Caspar Weinberger were also intended to participate. Robert McFarlane, who had assumed the position of National Security Advisor just two weeks earlier, realized the implications of such participation early in the exercise's planning and rejected it.