Which French king was captured at Poitiers in 1356?

The story behind the answer

At the Battle of Poitiers (1356), Edward, the Black Prince, shattered a larger French army and seized the reigning Valois monarch (r. 1350–1364), nicknamed “the Good.” Overconfident charges and disciplined English defensive tactics—especially dismounted men-at-arms supported by longbowmen—led to the king’s capture, a devastating blow to French leadership.

The aftermath reshaped the Hundred Years’ War: the Dauphin Charles governed as regent amid financial collapse, the Estates-General demanded reforms, mercenary “Free Companies” ravaged the countryside, and social unrest erupted in Paris and the Jacquerie (1358). The Treaty of Brétigny (1360) secured the king’s release at a staggering ransom and territorial concessions. That regent later became Charles V, who reversed French fortunes through careful strategy, avoiding pitched battles and favoring attrition and sieges.