He returned in 1263, at the invitation of the barons, who were now convinced of the king's hostility to all reform; and raised a rebellion with the avowed object of restoring the form of govern ment which the Provisions had ordained. For a few weeks it seemed as though the royalists were at his mercy; but he made the mistake of accepting Henry's offer to abide by the arbitration of Louis IX. of France. At Amiens, in Jan. 1264, the French king decided that the Provisions were unlawful and invalid. Montfort at once resumed the war, and thus exposed himself to accusations of perjury, from which he can only be defended on the hypothesis that he had been led to hope for a genuine compromise. Though merely supported by the towns and a few of the younger barons, he triumphed by superior generalship at Lewes (May 14, 1264), where the king, the Lord Edward, and Richard of Cornwall fell into his hands. Montfort used his victory to set up the govern ment by which his reputation as a statesman stands or falls. The weak point in his scheme was the establishment of a triumvirate (consisting of himself, the young earl of Gloucester and the bishop of Chichester) in which his colleagues were obviously figureheads. This flaw, however, is mitigated by a scheme, which he simul taneously promulgated for establishing a thorough parliamentary control over the executive, not excepting the triumvirs. The parliament which he summoned in 1265 was, it is true, a packed assembly; but it can hardly be supposed that the representation which he granted to the towns (see PARLIAMENT and REPRE SENTATION) was intended to be a temporary expedient.
The reaction against his government was baronial rather than popular; and the Welsh Marchers particularly resented Mont fort's alliance with Llewellyn of North Wales. Little consideration for English interests is shown in the treaty of Pipton which sealed that alliance (June 22, 1265). It was by the forces of the Marchers and the strategy of Edward that Montfort was defeated at Evesham (Aug. 4). For years after his death he was revered by the commons as a martyr, and the government had no little difficulty in reducing the remnants of his baronial supporters. He was undoubtedly harsh, masterful, and ambitious; but no mere adventurer could have won the friendship of such men as Adam Marsh and Grosseteste; their verdict of approval may be the more unhesitatingly admitted since it is not untempered with criticism.
The original authorities are those for the reign of Henry III. The best biographies are those by R. Pauli (trans. C. M. Goodwin, 1876) ; G. W. Prothero (1877) C. Bemont (1884). See also the letters of Adam de Marsh in J. S. Brewer's Monumenta franciscana, vol. i. (Rolls series, 1858) ; • H. R. Luard, Epistolae Roberti Grosseteste (Rolls series, 1861) ; F. S. Stevenson, Grosseteste (5899) ; W. H. Blaauw, The Barons' War (1871) ; T. S. Bateman, Simon de Montfort (1923) ; E. F. Jacob, Studies in the Period of Baronial Reform and Rebellion