The Battle of Agincourt (October 25, 1415) was a decisive English victory over the French in the Hundred Years' War.

Ten weeks prior to the battle, England's King Henry V had landed an expeditionary force of 11,000 in Normandy where he planned to take Harfleur before marching on Paris. They took Harfleur in September, but by then half of his troops had been lost to disease and battle casulties. Henry decided to move Northeast to Calais, the narrowest point on the English Channel, where his forces could return to England. However, large French forces blocked his line of advance to the north.

The French force, which totaled approximately 30,000 men, caught the exhausted English army at Agincourt. The French were very confident of victory, and spent the evening prior to battle carousing and taunting the English. The English, however, had a number of things in their favor. Throughout Europe, armies were typically made up of knights, and as many peasants as the local feudal levy could raise. But Henry's army was specially recruited; his men were well paid, highly disciplined, and well trained. Most of his army was made up of expert archers using the English longbow. Also, the French unwisely chose a narrow battlefield between two thick forests. This small space made large scale maneuvers difficult and helped offset the French advantage of their overwhelming numbers.

Henry arranged his troops carefully with his archers taking up positions on the flanks and between the men-at-arms. The French had arranged themselves into three dense lines flanked by the forests. As they advanced, the knights were forced into each other by the narrowing front formed by the two forests and made movement very difficult. As the heavily armored knights moved forward, they turned the rain-saturated ground into deep mud and the front ranks who were able to advance received the full effect of English archers. As more French knights entered the battle, they became so tightly bunched that some of them could barely raise their arms to strike a blow. At this decisive point, Henry commanded his lightly equipped and more mobile English archers to attack with swords and axes. As the battle progressed, the French became aware of the scale of the disaster. As word spread the French army started to slip away into the countryside and this quickly became a rout.