Henry IV (15 April 1367 20 March 1413), also known as Henry of Bolingbroke, was the King of England and Lord of Ireland from 1399-1413; before then, he was Earl of Derby, Duke of Hereford, and Duke of Lancaster. As King, he was the founder of the House of Lancaster, a cadet branch of The House of Plantagenet. Born in 1367 at Bolingbroke Castle in Lincolnshire, he was the son and heir of John of Gaunt, the Duke of Lancaster, and a grandson of Edward III. While he was neither the heir, not the spare to the throne, his father was the most powerful peer in the country at the time, as well as the wealthiest. Young Henry grew up as a prominent member of the royal court, where he was the boyhood companion of Richard The Second. The two young boys could not have been more different; Richard was a cultured man and a great patron of the arts, while Henry was a keen warrior and tournament champion, going on crusade to Lithuania to support The Teutonic Knights, before going on pilgrimage to Jerusalem and vowing to liberate it (something he never got around to). His relationship with his erstwhile best friend, cousin, and liege, the circumstances that led him to usurp Richard's throne, and the estrangement of The House of Plantagenet into competing factions, informed much of the political conflict that plagued England in the 15th Century.
The first cracks in their relationship emerged when John of Gaunt, Richard's benefactor, left England to pursue the throne of Spain, claiming it by right of his wife, the Infanta Constance of Castile. Long story short: with his protector, adviser, and political linchpin off trying to claim a kingdom for his own, Richard was more vulnerable than ever. In the years that Gaunt spent in Spain, Richard gathered a cohort of followers and royal favorites that aroused controversy among the English political. Some were of common birth and some were unpopular, but by appointing them to prestigious positions above the high magnates, he made powerful enemies. Among these were the Duke of Gloucester, the Earl of Arundel, the Earl of Warwick, the Earl of Nottingham, and Henry, the Earl of Derby. These five individuals dubbed themselves the "Lords Appellant" and launched an armed rebellion against Richard in 1387, where Henry crushed an army commanded by Robert de Vere, the Earl of Oxford and Richard's favorite, at Radcot Bridge. Richard was reduced to a figurehead, and one by one, the newly-formed Merciless Parliament of 1388 purged the court of all his supporters.
Richard and the Lords Appellant came to a rapprochement when John of Gaunt returned empty-handed from Spain. With his protector back in England, Richard was able to reassert some of his former power. More importantly to him, he was able to exact revenge. In 1397, he struck against the former Lords Appellant. Warwick was beheaded, Arundel was stripped of his lands and titles and imprisoned on the Isle of Man, and Gloucester was mysteriously murdered in Calais, likely by the King's command. In a classic case of keeping one's friends close, but their enemies closer, Richard not only pardoned Henry and the Earl of Nottingham, but he made them the Dukes of Hereford and Norfolk, respectively. The next year, however, Henry and Norfolk quarreled over the latter's involvement in having Gloucester killed. Richard, in turn, took the opportunity to banish both from England.
During his exile, John of Gaunt fell ill and died. This created a massive problem for Richard. For one, his most important servant had died, leaving him politically vulnerable. Secondly, the Lancastrian estates were vast, being worth the modern equivalent of over $100 billion , and all of that wealth, power, and prestige was going in the hands of his friend-turned-rival, Henry of Bolingbroke. Henry, now rightfully Duke of Lancaster, had a huge base of support in England, from all parts of society, and his accomplishments made him seem like The Paragon of everything a medieval Englishman ought to be: honest, soldierly, and chivalrous. Richard, in a half-baked attempt to combat this burgeoning problem head on, confiscated Henry's lands, and used the vast wealth to finance...an invasion of Ireland.
Henry's fortunes could not have been better. Assembling an army, he landed in Ravenspur in the north of England and began gathering support as he marched. His claim that he was only returning to England to assume his rightful title as Duke of Lancaster struck a chord with the disaffected nobility of England, and at the time, Henry might have meant it. Richard's arbitrary and autocratic behavior in seizing the Lancastrian estates made every noble fear that their own estates could be taken at any time, for any reason. They flocked to the Duke of Lancaster, and in time, Henry had even the support of his uncle, Edmund of York, the Percy family of Northumberland. Richard was blindsided, and soon after his return to England, he was captured by Henry's men and held at Pontefract Castle.
With the King of England as his hostage, Henry now faced the problem of what to do with Richard. The king was a ruthless man, and allowing him to regain power would make the House of Lancaster a target for the rest of his reign. More importantly, not having someone on the throne would have been disastrous, and the only other heirs were small boys. Killing a king would have been an unthinkable crime, and Richard was not only a king, but Henry's boyhood companion. Whatever his feelings on the matter, it seems as though Henry was satisfied with Richard resigning his crown and living in captivity. Henry of Bolingbroke became Henry IV of the House of Lancaster. But then, in 1400, a year into his reign, supporters of Richard launched a rebellion, and after it was crushed, Richard starved to death in his cell. Whether Henry ordered it or not has never been conclusively confirmed, but his cousin's death wracked him with guilt.
More seriously, it also turned key allies against him. As a usurper, what he had done to Richard could easy be done to him. In 1403, Sir Edmund Mortimer, a descendant of Edward III through his second son Lionel, was captured leading an expedition against Owain Glyndwr of Wales, a rebel leader who styled himself Prince of Wales. When Henry was considering whether to ransom him, Mortimer married Glyndwr's daughter, and Henry refused to ransom a perceived traitor back to England. This angered the Percy family, led by the Earl of Northumberland and Sir Henry "Hotspur" Percy, who were already resentful of Henry for not fulfilling promises of land, and for perjuring himself regarding his oath — he had claimed Lancaster, but he had taken the Crown. The Percys, Glyndwr, and Mortimer joined forces and Northumberland, Wales, Cheshire, and Shropshire rose in rebellion. At Shrewbury in 1403, his army and the rebels engaged in a bloody battle that left thousands dead. Henry himself was nearly killed and his son, Henry of Monmouth, the future Henry V, took an arrow to the face. Hotspur was also struck, and killed by an arrow, and his rebellion was broken. Over the next ten years, Monmouth would lead his father's army in destroying the rebels. The Percys were crushed, and Sir Edmund Mortimer was defeated in 1408 at Harlech Castle. Owain Glyndwr continued to be a thorn in England's side until 1415, when he disappeared.
Approaching the end of his life, Henry was stricken by a debilitating skin disease, thought now to be leprosy. He died in 1413, regretting Richard's death, and in fear for the state of his soul. The lingering political crisis that his usurpation caused would later give rise to the Wars of the Roses and the usurpation of his grandson, Henry VI.