Edmund Beaufort, second duke of Somerset (c.1406-1455) was a major supporter of Henry VI in the period before the outbreak of the Wars of the Roses, but he was killed at St. Albans in the first battle of the wars.
Like so many of the major players in the Wars of the Roses Somerset was a descendent of Edward III. Later in life, John of Gaunt, duke of Lancaster, one of Edward's son, had four children with his mistress Katherine Swynford. In 1396 the widowed Gaunt married Swynford, and their by then adult children were legitimised. The eldest of the children, John Beaufort, was made earl of Somerset in 1397.
The new earl was the half-brother of John of Gaunt's oldest son, Henry Bolingbroke. In 1399 Bolingbroke returned from exile to overthrow Richard II, becoming Henry IV, the first of the Lancastrian kings. Somerset was now close to the throne, and he and his descendents would be loyal supporters of the Lancastrian dynasty.
John Beaufort had six children. Edmund was his fourth son, but none of his older brothers was long-lived. His father died in 1410 and was succeeded by his oldest son, Henry Beaufort. Henry died in 1418 and was succeeded by his brother John, who became the first duke of Somerset. The third son, Thomas Beaufort, count of Perche, died in 1431, so when John died in 1444 Edmund became earl of Somerset. He didn't become the second duke of Somerset until 1448 (sometimes he is recorded as the first duke of a second creation of the duchy because of the four year gap).
Somerset's military career became before he inherited his family estates. He fought in France from the 1420s, recaptured Harfleur in 1440 and lifted a siege of Calais in 1442. He was made earl of Dorset in 1442 and Marquess of Dorset in 1443. Despite his successes and titles, Somerset's own income was a fraction of that of his main rivals. Somerset was an unpopular man, and one of the causes of that unpopularity was the large number of Royal posts that he was given in an attempt to raise his income to a suitable leve.
In December 1447 he succeeded Richard, duke of York, as lieutenant of France. This appointment came just as the French were preparing for the conquest of Normandy, which took place with unexpected speed in 1449-50. Somerset was unable to stop them, and this failure made his very unpopular in England. Somerset's conduct in Normandy wasn't terribly impressive. On 29 October 1449 he has surrendered Rouen, the capital, and paid a large ransom for the safety of his family and retinue while on 1 July 1450 he surrendered Caen.
The failures in France also played a part in the outbreak of Jack Cade's Rebellion in 1450. This led to the overthrown of William de la Pole, duke of Suffolk, then Henry VI's chief minister. Somerset replaced him, and for the next two years played the chief role in the government. Amongst the titles he gained during this period was captain of Calais, which gave him command of the most significant permanent military force under English control.
By now Somerset was involved in a feud with Richard of York. In February 1452 York issued a condemnation of Somerset, charging him with plotting to destroy York's family and with responsibility for the loss of Normandy. York attempted to raise an army, but failed very little support. His small force reached Dartford in late February, after failing to get access to London. After a standoff York was forced to back down. His dispute with Somerset was put to arbitration, but the panel was dominated by Somerset's friends and nothing came of it. Somerset's position had survived this crisis, but he was soon to face a far more serious problem.
In 1453 Henry VI suffered his first bout of mental illness. Although the council attempted to prevent it, Richard of York eventually became Protector. York resented Somerset's closeness to the throne, his appointment to command in France and his military failures. Somerset was committed to the Tower of London, where may eventually have been tried for his failures in France. York replaced Somerset as Captain of Calais, although struggled to actually gain access to the town.
Henry VI recovered at the end of 1454. The Protectorate came to an end, Somerset was released and the charges against him were dropped. In 1455 he was restored as Captain of Calais.
York believed that the court would soon move against him. He now had more allies than in 1452, and had gained the active support of Richard Neville, earl of Salisbury and his son Richard Neville, earl of Warwick. They raised an army and moved south.
The Royal army moved out of London, but only reached St. Albans. On 22 May 1455 York and his allies attacked the Royalists at the First Battle of St. Albans. At first the Royalists were able to keep them out of the town, but eventually they broke into the town. Very few of the noblemen were killed in the battle, but amongst them was Somerset. He was trapped in the Castle Inn after the collapse of the Lancastrian position. The inn was surrounded. Somerset realised that his cause was lost and decided to launch a final assault from the inn. He is said to have killed four men before he was overwhelmed and killed himself.
Somerset was succeeded by his son Henry Beaufort, third duke of Somerset (1436-1464). Henry considered his father's death to have been murder and became an implacable enemy of the House of York.