http://www.legis.state.wi.us/rsb/Statutes.html - PDF!
939.48 Self−defense and defense of others. (1) A person
is privileged to threaten or intentionally use force against
another for the purpose of preventing or terminating what the person
reasonably believes to be an unlawful interference with his or
her person by such other person. The actor may intentionally use
only such force or threat thereof as the actor reasonably believes
is necessary to prevent or terminate the interference. The actor
may not intentionally use force which is intended or likely to cause
death or great bodily harm unless the actor reasonably believes
that such force is necessary to prevent imminent death or great
bodily harm to himself or herself.
(2) Provocation affects the privilege of self−defense as follows:
(a) A person who engages in unlawful conduct of a type likely
to provoke others to attack him or her and thereby does provoke
an attack is not entitled to claim the privilege of self−defense
against such attack, except when the attack which ensues is of a
type causing the person engaging in the unlawful conduct to reasonably
believe that he or she is in imminent danger of death or
great bodily harm. In such a case, the person engaging in the
unlawful conduct is privileged to act in self−defense, but the person
is not privileged to resort to the use of force intended or likely
to cause death to the person’s assailant unless the person reasonably
believes he or she has exhausted every other reasonable
means to escape from or otherwise avoid death or great bodily
harm at the hands of his or her assailant.
(b) The privilege lost by provocation may be regained if the
actor in good faith withdraws from the fight and gives adequate
notice thereof to his or her assailant.
(c) A person who provokes an attack, whether by lawful or
unlawful conduct, with intent to use such an attack as an excuse
to cause death or great bodily harm to his or her assailant is not
entitled to claim the privilege of self−defense.
There are a dozen or so 'annotations' to case law in the source document.