In his youth, Henry gained military experience fighting the Welsh during the revolt of Owain Glyndŵr and against the powerful aristocratic House of Percy of Northumberland at the Battle of Shrewsbury. Henry later came into political conflict with his father, Henry IV, whose health was increasingly precarious from 1405 onward and who had consequently started to withdraw from government functions. After his father's death in 1413, Henry assumed control of the country and asserted the pending English claims to the French throne.
In 1415, Henry embarked on war with France in the ongoing Hundred Years' War (1337–1453) between the two nations. His military successes culminated in his famous victory at the Battle of Agincourt (1415) and saw him come close to conquering France. Taking advantage of political divisions within France, he conquered large portions of the kingdom and Normandy became English for the first time in 200 years. After months of negotiation with Charles VI of France, the Treaty of Troyes (1420) recognised Henry V as regent and heir apparent to the French throne and he was subsequently married to Charles's daughter, Catherine of Valois (1401–1437).
Following Henry V's sudden and unexpected death in France two years later, he was succeeded by his infant son, who reigned as Henry VI in England and Henry II in France. The lack of unity and of a political consensus in Henry VI's regency government, coupled with Henry VI's ineffectual rule, would jeopardize Henry V's gains and undermine English rule in France.
Henry was born in the tower above the gatehouse of Monmouth Castle, Monmouth, Principality of Wales and for that reason was sometimes called Henry of Monmouth. He was the son of 20-year-old Henry of Bolingbroke (later Henry IV of England) and 18-year-old Mary de Bohun. He was also the grandson of the influential John of Gaunt and great-grandson of Edward III of England. At the time of his birth, Richard II of England, his cousin once removed, was king. As he was not close to the line of succession to the throne, Henry's date of birth was not officially documented; it is generally thought to be 9 August or 16 September of either 1386 or 1387. His grandfather, John of Gaunt, was the guardian of the king at that time.
Upon the exile of Henry's father in 1398, Richard II took the boy into his own charge and treated him kindly. The young Henry accompanied King Richard to Ireland. While in the royal service, he visited Trim Castle in County Meath, the ancient meeting place of the Irish Parliament. In 1399, Henry's grandfather died. In the same year, King Richard II was overthrown by the Lancastrian usurpation that brought Henry's father to the throne and Henry was recalled from Ireland into prominence as heir apparent to the Kingdom of England. He was created Prince of Wales at his father's coronation and Duke of Lancaster on 10 November 1399, the third person to hold the title that year. His other titles were Duke of Cornwall, Earl of Chester and Duke of Aquitaine. A contemporary record notes that during that year, Henry spent time at The Queen's College, Oxford under the care of his uncle Henry Beaufort, the chancellor of the university. From 1400 to 1404, he carried out the duties of High Sheriff of Cornwall.