The French army moved forward late in the afternoon, around 4pm after it had formed up. As it advanced, a sudden rainstorm broke over the field of battle. The English archers de-strung their bows to avoid the strings becoming damaged; the Genoese with their crossbows could take no such precautions, resulting in damage to their weapons. The crossbowmen began their advance, however they had left their pavises back in the baggage train, and thus had no means of protection as they loaded their weapons. The Genoese moved within range and discharged their weapons. Damaged by the rain, the slackened crossbows had little effect on the English line. The English archers shot their bows in retaliation, inflicting heavy casualties on the Genoese, causing them to retreat. The knights and nobles following in Alençon's division, seeing the routed mercenaries, hacked them down as they retreated. Froissart writes of the event:
The English, who were drawn up in three divisions and seated on the ground, on seeing their enemies advance, arose boldly and fell into their ranks. The clash of the retreating Genoese and the advancing French cavalry threw the army into disarray. The longbowmen continued to discharge their bows into the chaos, while five Ribaldis, early cannon, added to the confusion, though it is doubtful that they had inflicted any significant casualties. The longbowmen loosed volleys of grey goose feathered arrows to extreme range, ten or more every minute. It was said, "Arrows fell like snow". Men and horses fell. Those reaching the bottom of the V were engaged at shorter range, where the longbow pierced armour.
With the Genoese neutralised, the French cavalry charged the English ranks, however, the slope and obstacles laid by the English disrupted the charge. The continued hail of longbow arrows inflicted mounting losses upon the knights, blocking successive waves of advance by the following ranks. The massed ranks could not break the English position, which subjected them to a relentless barrage of arrows, making many of the horses casualties. The Black Prince's division was hard pressed by the French attack, however Edward refused to send help with the comment; "Let the boy win his spurs".
The French cavalry made repeated attempts to charge up the slope, however with each successive wave more losses were sustained. In the course of the battle, the blind king John of Bohemia was struck down attacking the Black Prince's position. The struggle continued well into the night when Philip abandoned the field of battle. Philip had his horse killed from underneath him twice during the battle and may have taken an arrow to the jaw. His sacred and royal banner, the Oriflamme, which when raised meant that no quarter was to be given to the enemy, was also captured and taken, one of the five occasions this occurred during the banner's century spanning history. The battle ended soon after the French king fled, the remaining men-at-arms running from the battle.
By midnight, Philip's brother, Charles II of Alençon and his allies, King John of Bohemia and the Count of Flanders, Louis II of Nevers, as well as 1,500 other knights and esquires were dead. The men-at-arms and Genovese archers were not counted but estimates of the total slaughter varied between five and fifteen thousand. King Philip himself escaped with a wound. Edward resumed his march, now with prisoners for ransom, towards Calais, which he besieged without interruption and eventually took. After the battle, the blind King of Bohemia, was found as he had ridden into battle, chained between his knights less they loose him. All were present; all were dead, all clustered around their King. The Prince of Wales took his arms and wore his crest, three ostrich feathers girdled in a crown; he and all Welsh Regiments and military units have done so ever since.
The battle crippled the French army's ability to come to the aid of Calais, which was besieged by Edward's army the following month. Calais fell after a year-long siege and became an exclave of England, remaining under English rule until 1558.