At the heart of the plot of this opera is a complicated series of historical events beginning at the end of the twelfth century. King Philip Augustus of France (Philip II of France) married the Danish princess Ingeborg in 1193. For unknown reasons, he separated from her the day after the wedding and sought an annulment from Pope Celestine III. Ingeborg, however, insisted that the marriage had been consummated, and that she was his wife and the rightful Queen of France. Philip ultimately obtained an annulment through an assembly of French bishops. He then sought to marry Marguerite, daughter of William I, Count of Geneva, but she was kidnapped on the way to Paris by Thomas I of Savoy, who married her instead. Ultimately, in 1196 Philip married Agnes of Merania ("la straniera"), the daughter of a nobleman, Bertold IV of Dalmatia. Denmark continued to complain about Philip's treatment of Ingeborg and in 1200 Pope Innocent III required Philip to take her back, rendering him essentially a bigamist and subject to excommunication. Agnes died in 1201, however, ending the threat of excommunication.