“The particular no-duty-to-retreat walkdown that occurred in the public square of the remote southwest Missouri town of Springfield in July 1865 received national publicity, and in its aftermath the duty to retreat became a legal issue. Whether or not it was actually the first walkdown, the gunfight in Springfield was the effective beginning of the walkdown tradition, for it was the first to receive wide public recognition as such._,i In this case, the victorious gunfighter was Eisenhower's fondly remembered hero, Wild Bill Hickok.”