It was a defining moment in the history of weapons development and the future of man and machine. A computer had reported that a thousand-strong Soviet ICBM attack was under way. And a human, in this case Air Marshal Charles Roy Slemon, used his judgment to intervene and to overrule. At J-Site, the ARPA 474L System Program Office worked with technicians to teach the BMEWS computers to reject echoes from the moon.