In the field of nuclear warheads size matters. Building a basic bomb is not difficult.
Small warheads enable more than one bomb to be placed on a single missile.
They also enable more effective warheads to be placed on lighter mobile missiles. Both Russia and the United States have deployed such technology. But China has not and is struggling to catch up. The possibility that a Los Alamos computer expert could have supplied Beijing with the details is thus a security lapse of major proportions. The story is also likely to have an explosive impact upon the Clinton Administration's efforts to defend its policy of engagement with China.