What gave England an immense advantage in the war?

Directions: Read the following passage and answer the question that follows.

By the Salic law, as the lawyers called it, the crown was given, on the death of Charles IV, to Philip, Count of Valois, son to a brother of Philip IV, but it was claimed by Edward III of England as son of the daughter of Philip IV. Edward satisfied himself, however, with the mere declaration of his self-importance, until Philip annoyed him by attacks on the borders of Guienne, which the French kings had long been wanting to complete their possession of the South, and by demanding the surrender of Robert of Artois, who, being disappointed in his claim to the county of Artois by the judgment of the Parliament of Paris, was practising by sorcery on the life of the King of France. Edward then declared war, and his supposed right caused a century of warfare between France and England, in which the broken, down-trodden state of the French farmers gave England an immense advantage. The knights and squires were fairly matched; but while the English yeomen were strong, staunch, and trustworthy, the French were useless, and only made a defeat worse by robbing the fallen on the each side alike.