The civil war, which Diniz had waged with his father, was followed on his accession to the throne by a fierce struggle between Diniz and his brother Affonso, who disputed his legitimacy, which ended in a compromise. He then married, in 1281, Donna Isabel, daughter of Pedro III. of Aragon, who was canonized in later years for her pure and unselfish life. His reign is only marked by one war with Sancho IV. and Ferdinand IV. of Castile and Leon, which was terminated in 1297 by a treaty of alliance, according to the terms of which Ferdinand IV. married Constance, daughter of Diniz, while Affonso, the heir to the throne of Portugal, married Beatrice of Castile, the sister of Ferdinand, but his reputation none the less stood very high in the peninsula, as is shown by his being chosen in 1304 to act as joint arbitrator with the King of Aragon between Ferdinand of Castile and his cousin, Ferdinand of Lacerda. Still more interesting are the king’s relations with Edward I. of England, with whom he exchanged many letters, chiefly on commercial subjects, and with whom he made a treaty of commerce in 1294. He had much correspondence also with Edward II., and in particular he agreed with the English king in 1311 that the Knights Templars had been greatly maligned. When that famous order was suppressed by Pope Clement V. in compliance with the wishes of Philip le Bel of France, Dom Diniz took a course which demonstrated his political wisdom. He recollected the great services which the military orders had formerly rendered to Portugal, and bore in mind their influence and power, and he therefore founded the Order of Christ in conjunction with Pope John XXII. in 1319, and invested it with all the property of the Templars, thus at once obeying the Pope and avoiding a serious disturbance at home. He showed the same wisdom with regard to the knights of Santiago in Portugal, whom he persuaded Pope Nicholas IV. to release from the control of the Grand Master of the Order in Castile, and to establish on an independent footing.