The Battle of Crécy, was an important English victory during the Hundred Years' War. 

The battle was fought on 26 August 1346 near Crécy, in northern France. An army of English, Welsh and allied troops from the Holy Roman Empire led by Edward III defeated a much larger army of French, Genoese and Majorcan troops led by Philip VI of France. Emboldened by the lessons of tactical flexibility and utilisation of terrain learned from the earlier Saxons, Vikings and the recent battles with the Scots, the English army, despite being heavily outnumbered by the French, won a decisive victory.

The battle saw the rise in power of the longbow as the dominant battlefield weapon, whose effects were devastating when used en-masse. Crécy also saw the use of some very early cannon by the army. The combined-arms approach of the English, the new weapons and tactics used, which was far more focused on the infantry than previous battles in the middle-ages and the killing of incapacitated knights by peasantry after the battle has led to the engagement being described as "the beginning of the end of chivalry".

The battle crippled the French army's ability to come to the aid of Calais, which fell to the English the following year. Calais would remain under English rule for over two centuries, falling in 1558. Upon the death of the French monarch Charles IV in 1328, the throne was legally supposed to pass to Edward III of England, the closest male relative. A French court, however, decreed that the closest relative of Charles was his first cousin, Philip, Count of Valois. Philip was crowned as Philip VI of France.

Edward II won several naval battles before returning to England to raise more funds for a future campaign and to build an army. On 11 July 1346, Edward set sail from Portsmouth with a fleet of 750 ships and an army of 15,000 men. With the army was Edward's sixteen-year-old son, Edward of Woodstock, a large contingent of Welsh soldiers and longbowmen, including those from Llantrisant and allied knights and mercenaries from the Holy Roman Empire. The army landed at St. Vaast la Hogue, 20 miles from Cherbourg. The intention was to undertake a massive chevauchée across Normandy, plundering its wealth and severely weakening the prestige of the French crown. Carentan, Saint-Lô and Torteval were all razed, after which Edward turned his army against Caen, the ancestral capital of Normandy. The English army sacked Caen on 26 July, plundering the city's huge wealth. Moving off on 1 August, the army marched south to the River Seine, possibly intending to attack Paris. The English army crossed the Seine at Poissy, however it was now between both the Seine and the Somme rivers. Philip moved off with his army, attempting to trap and destroy the English force.

Attempting to ford the Somme proved difficult; all bridges were either heavily guarded or burned. Edward vainly attempted to probe the crossings at Hangest-sur-Somme and Pont-Remy before moving north. Despite some close encounters, the pursuing French army was unable to bring to bear against the English. Edward was informed of a tiny ford on the Somme, likely well-defended, near the village of Saigneville called Blanchetaque.

On 24 August, Edward and his army successfully forced a crossing at Blanchetaque with few casualties. It was said that the Welsh longbowmen had played a pivotal role to achieve this. Such was the French confidence that Edward would not ford the Somme, the area beyond had not been denuded, allowing Edward's army to resupply and plunder; Noyelles-sur-Mer and Le Crotoy were burned. Edward used the respite to prepare a defensive position at Crécy-en-Ponthieu while waiting for Philip to bring up his army. The position offered protection on the flanks by the River Maye to the west, and the town of Wadicourt to the east, as well as a natural slope, putting cavalry at a disadvantage.

Edward deployed his army facing south on a sloping hillside at Crécy-en-Ponthieu; the slope putting the French mounted knights at an immediate disadvantage. The left flank was anchored against Wadicourt, while the right was protected by Crécy itself and the River Maye beyond. This made it impossible for the French army to outflank them. The army was also well-fed and rested, putting them at an advantage over the French, who did not rest before the battle.

The English army was led by Edward III, primarily comprising English and Welsh troops along with allied Breton and German mercenaries. The exact size and composition of the English force is not accurately known. Andrew Ayton suggests a figure of around 2,500 men-at-arms; nobles and knights, heavily armoured and armed men, accompanied by their retinues. The army contained around 5,000 longbowmen, 3,000 hobelars (light cavalry & mounted archers) and approximately 3,500 spearmen.[8] Clifford Rodgers suggests 2,500 men-at-arms, 7,000 longbowmen, 3,250 hobelars and 2,300 spearmen.[9] Jonathon Sumption believes the force was somewhat smaller, based on calculations of the carrying capacity of the transport fleet that was assembled to ferry the army to the continent. Based on this, he has put his estimate at around 7,000–10,000.

Welsh freemen were mercenaries, soldiers of fortune and no one's vassals, in sharp contrast to the feudal English (and French) cavalry, where knights did most of the fighting, each "lance" supported by a team of grooms, armourers and men at arms under its lance-corporal, vassals serving at the command of their lord, giving unpaid the military service that their land holding demanded. Welsh freemen, like their Genoese counterparts - and like the Gurkhas today - were there for pay (six pence per day) and booty. The change Crécy made to warfare, the European balance of power and the social order cannot be exaggerated and was permanent. It took fifty years before cavalry - with new, expensive horse-armour - regained anything like its former pre-eminence. The value of the longbow as a long-range killing weapon re-established the importance of skilled, professional foot-soldiers, leading to mercenary armies and a balance between infantry and cavalry. English and later British power became of Continental importance.

The power of Edward's army at Crécy lay in the massed use of the longbow; a powerful tall bow made primarily of yew. Knights on horseback - heavy cavalry - had dominated the battlefield since the later years of the Roman Empire , lost their dominance. Infantry had been unable to withstand the terrifying and irresistible charge of a massed formation of armoured knights on heavy horses with long lances that could reach over shields and outreach pikes. The new weapon, introduced by Henry III of England 100 years before, used by Welsh archers serving Edward I at the battle of Falkirk in 1298 and Edward III against Scottish knights at Halidon Hill in Berwickshire in 1333, had never before been used to its full potential. It had taken decades to work out how to maximise its range and power, perfect its accuracy and develop tactics and training to exploit it to the full. Edward III later declared in 1363 that archery had to be practised by law, banning other sports to accommodate archery instead.

The French army was led by Philip VI and the blind John of Bohemia. The exact size of the French army is less certain as the financial records from the Crécy campaign are lost, however there is a prevailing consensus that it was substantially larger than the English. The French army likely numbered around 30,000 men. 

The English army was deployed in three divisions, or "battles". Edward's son, Edward, the Prince of Wales commanded the vanguard with John de Vere, the Earl of Oxford, Thomas de Beauchamp, the Earl of Warwick and Sir John Chandos. This division lay forward from the rest of the army and would bear the brunt of the French assault. Edward himself commanded the division behind, while the rear division was led by William de Bohun, Earl of Northampton. Each division composed of spearmen in the rear, men-at-arms in the centre and the longbowmen arrayed in front of the army in a jagged line. Edward ordered his men-at-arms to fight on foot rather than stay mounted. The English also dug a series of ditches, pits and caltrops to maim the French cavalry.

The French army came north from Abbeyville, the advance guard of his army arriving at the Crécy ridgeline at around midday on 26 August. After reconnoitring the English position, it was advised to Philip that the army should encamp and give battle the following day. Philip met stiff resistance from his senior nobles and was forced to concede that the attack would be made that day. This put them at a significant disadvantage; the English army was well-fed after plundering the countryside and well-rested, having slept in their positions the night before the battle. The French were further hampered by the absence of their Constable. It was the duty of the Constable of France to lead its armies in battle, however, the Constable Raoul II of Brienne, Count of Eu had been taken prisoner when the English army sacked Caen, depriving them of his leadership. Philip formed up his army for battle; the Genoese under Antonio Doria and Carlo Grimaldi formed the vanguard, followed by a division of knights and men-at-arms led by Charles II, Count of Alençon accompanied by the blind King John of Bohemia. The next division was led by Rudolph, Duke of Lorraine and Louis II, Count of Blois, while Philip himself commanded the rearguard.