Henry V gained military and administrative experience while prince of Wales under Henry IV. He fought against the Welsh rebellion led by Owain Glyndŵr and was seriously wounded at Shrewsbury in 1403. He succeeded his father in March 1413 and moved quickly to consolidate authority.

Henry sought to manage aristocratic divisions and enforce religious order, including suppression of Lollard resistance associated with Sir John Oldcastle. He revived English claims in France, using diplomacy and military preparation to pursue both territorial recovery and a dynastic claim. Before departure in 1415, he suppressed the Southampton conspiracy. His invasion captured Harfleur after a costly siege, but disease weakened the army. Attempting to reach Calais, he encountered a French force at Agincourt on October 25 and won a major victory through defensive positioning, archery, and French tactical difficulties.

The success enhanced his prestige without immediately conquering France. Henry returned in 1417 for a more sustained campaign, capturing towns and strongholds in Normandy. Rouen surrendered in 1419 after a siege that subjected civilians to severe suffering. French internal divisions between Burgundian and Armagnac factions aided his advance. The Treaty of Troyes in 1420 recognized Henry as heir and regent to Charles VI and excluded the dauphin from that arrangement. Henry married Catherine of Valois, joining the settlement to a dynastic alliance. The treaty did not secure universal French acceptance, and warfare continued against supporters of the dauphin.

Henry combined campaigning with close attention to administration and finance, drawing resources from Parliament, royal revenue, and the conquered territories. His authority depended on commanders and officials operating across both kingdoms. In 1421 Catherine gave birth to their son, the future Henry VI. Henry continued military operations but became ill and died at Vincennes in August 1422, before Charles VI. His infant son inherited the English crown and the contested claim to France under the treaty. The resulting minority and continued French resistance exposed the fragility of his achievements. His reputation as a victorious king was later enlarged by Shakespeare and nationalist memory, while the historical reign involved costly occupation, religious coercion, and a succession settlement that ultimately failed to unite the kingdoms permanently.