In 1345, Jeanne Gourmont, daughter of Guillaume de Bois Gourmont married Jean de la Jaille. The castle and estates of Ranton were part of Jeanne's dowry, and Jean de la Jaille became the Lord of Ranton. He was already an experienced and valued knight: he had been born in 1324 and brought up in a privileged environment in which the values of medieval chivalry dominated. He first appeared in the rolls of the King's army at the age of 16 when he is recorded as leading a troop of three young squires to join the army in Flanders. He first saw action at the head of a troop of twenty soldiers at the Battle of Saint-Omer on 24 June 1340 between an Anglo-Flemish army commanded by Robert III of Artois and the French under Eudes IV, Duke of Burgundy.