Bartholomew’s day in 1572, when some 20,000 Huguenots were slaughtered. The French crown’s participation in the massacre (through the young King Charles IX’s domineering mother, Catherine de Medici), inspired Beza to write Concerning the Power of Magistrates (1574). Here, Beza argued that if monarchs behaved tyrannically, the lesser political authorities of the realm could lawfully restrain them, by force if necessary. This became the standard Reformed view, acted on not just by Huguenots in France,