St. Brice’s Day Massacre On this date over a millennium past, according to the chronicle of John of Wallingford, King Ethelred the Unready of England conducted a massacre of Danes living in the realm. The character of this sanguinary event — named after a fourth-century French bishop whose feast day Nov. 13 happens to be — lies half-buried in history’s shifting sands. Surely the slaughter of every Dane in a Britain then very much in the Scandinavian orbit would have been not only morally reprehensible but logistically unimaginable. The accepted, albeit sketchy, story has it that to consolidate his own authority — or to check an actual or suspected plot against him — Ethelred ordered the surprise apprehension and summary execution of some sizable number of Danish lords and mercenaries. British historian Thomas Hodgkin characterizes it as a sort of coup d’etat . On this date, it was the Danes who were unready for Ethelred. But what...