In 1841, U.S. Secretary of State Daniel Webster
"articulated a set of demanding criteria for acting with a 'necessity of
self-defense'—in particular for a legitimate use of preemptive force.
Preemption, Webster said, is justified only in response to an imminent threat;
moreover, the force must be necessary for self-defense and can be deployed only
after nonlethal measures and attempts to dissuade the adversary from acting had
failed. Furthermore, a preemptive attack must be limited to dealing with the
immediate threat and must discriminate between armed and unarmed, innocent and
guilty."