Henry abandoned plans to attack Paris after the victorious but costly siege of Harfleur, in which one-third of his army died of dysentery. On October 25, 1415—the feast day of St. Crispin—Henry’s army defeated a much larger French force at Agincourt. Henry’s army of about 6,000 battled up to 30,000 French soldiers, who were forced by the terrain to advance in narrow formations that made them easy targets for Henry’s archers. The French advance was impeded by mud and their own mounting dead. All the while, Henry kept control of the battle, encouraging his troops and fighting hand-to-hand.
After the English took so many prisoners that Henry worried they might overpower their guards, he violated the rule of war by ordering their immediate execution. All told, the French lost as many as 7,000, while the English dead numbered at most a few hundred. Though not militarily decisive, the victory at Agincourt won Henry important allies and gained him a hero’s welcome on his return to England.