This event is known in history as the massacre of St. Bartholomew. The massacre was in no sense a premeditated affair. It was a sudden outburst of popular indignation brought about by the machinations of the queen-mother, and was neither encouraged nor approved by the bishops of the Catholic Church. The king presented himself before the Parliament of Paris on the day following the massacre, and declared that he alone was responsible for what had happened. He explained that a plot had been formed against his life and that he had taken the only measures that it was possible for him to take. This was the account of the affair that was forwarded to the French diplomatic representatives abroad, and which they gave at all courts to which they were accredited. Gregory XIII., acting on the report of the French ambassador, ordered that a /Te Deum/ should be sung in thanksgiving for the safety of the king and royal family, and not, as has been so often alleged, as a sign of rejoicing for the murder of the Calvinists. On the contrary he was deeply pained when he learned the true state of affairs. The massacre of St. Bartholomew was indeed unjustifiable, but it was done neither to promote religion nor at the instigation of the Church. It was merely political in its object as far as the king and the queen-mother were concerned, and it was a sudden popular outburst in so far as the citizens of Paris or the people of the country took part in it. In judging the responsibility and blame for what took place nobody can put out of mind the terrible excesses, of which the Huguenots had been guilty during their long struggle against their own countrymen. The German Lutherans, who looked upon the slaughter as a judgment from Heaven on the Calvinist heretics, were rejoiced at their execution.[8] The Huguenots flew to arms to avenge their brethren who had fallen, and the fourth civil war began. The Duke of Anjou laid siege to their strongest fortress, La Rochelle, but failed to take it, and on his election as King of Poland (1573) a treaty was concluded according to which the Huguenots were allowed free exercise of their religion. A large number of French politicians were at last growing tired of a struggle which was costing their country so dearly, and were anxious to conclude peace even though it were necessary to yield to the demands of the Huguenots. At the head of this party stood some of the most powerful nobles of France including the Duc d'Alencon, and when on the death of Charles IX. the Duke of Anjou succeeded as Henry III. (1575-89) his sympathies were entirely with the party of the moderates as against the extremists of both sides. By the terms of the Peace of Beaulieu (1576) the Huguenots were assured of complete freedom except in Paris and at the French Court, and of full civil rights, and as a guarantee of good faith they were continued in possession of their fortresses.