On both occasions, he played the peacemaker, and this sympathetic part, combined with his own pleasant manners, an engaging personality, a handsome person with bright eyes made him a popular royal favorite. In 1656, he was sent to command in Flanders, then in revolt against his own sovereign. At the storming of the French camp at Battle of Valenciennes (1656) in 1656, Don Juan Jose displayed great personal courage at the head of a brilliantly executed cavalry charge that caught the French totally by surprise. When, however, he took a part in the leadership of the army at the battle of the Dunes, fought against the French under Turenne and the British forces sent by Cromwell, he was decisively defeated and failed to raise the siege of Dunkirk, in spite of the efforts of Condé, whose invaluable advice he neglected, and the stubborn fight put up by his own troops.