"Muret is a little town to the southwest of Raymond’s capital, standing on the Garonne above stream, a day’s march from Toulouse itself. The huge Spanish host, which had no direct interest in the heresy itself but a strong interest in weakening the power of the French, was encamped in the flat country to the south of the town of Muret. As against them the only active force available was one thousand men under Simon de Montfort. The odds seemed ridiculous— one to one hundred. It was not nearly as bad as that, of course, because the thousand men were picked, armed, mounted nobles. The mounted forces in the Spanish host were probably not more than three or four times as great, the rest of the Spanish body being footmen, and many of them unorganized. But even so the odds were sufficient to make the result one of the most astonishing things in history.
It was the morning of the 13th of September, 1213. The thousand men on the Catholic side, drawn up in ranks with Simon at their head, heard Mass in the saddle. The Mass was sung by St. Dominic himself. Only the leaders, of course, and a few files could be present in the church itself where all remained mounted, but through the open doors the rest of the small force could watch the Sacrifice. The Mass over, Simon rode out at the head of his little band, took a fetch round to the west and then struck with a sudden charge at the host of Peter [of Aragon], not yet properly drawn up and ill-prepared for the shock. The thousand northern knights of Simon destroyed their enemies altogether. The Aragonese host became a mere cloud of flying men, completely broken up, and no longer in being as a fighting force. Peter himself was killed......
As for the Albigensian heresy itself, it was attacked politically both by civil and by clerical organizations, as well as by arms. The first Inquisition arose from the necessity of extirpating the remnants of the disease. (It is significant that a man pleading his innocence had only to show that he was married to be acquitted of the heresy! It shows what the nature of the heresy was.)
Under the triple blow of loss of wealth, loss of military organization, and a thoroughly organized political rooting out—this Manichean thing seemed in a century to have disappeared. But its roots ran underground, where, through the secret tradition of the persecuted of from the very nature of the Manichean tendency, it was certain to re-arise in other forms. It lurked in the central mountains of France itself and cognate forms lurked in the valleys of the Alps. It is possible to trace a sort of vague continuity between the Albigensians and the later Puritan groups, such as the Vaudois, just as it is possible to trace some sort of connection between Albigensian and the earlier Manichean heresies. Bit the main thing, the thing which bore the Albigensian name—the peril which had proved so nearly mortal to Europe—had been destroyed."
-Hilaire Belloc in The Great Heresies.