Thomas, 2nd Earl of Lancaster in the context of "Earl of Derby"

The House of Lancaster was a cadet branch of the royal House of Plantagenet. The first house was created when King Henry III of England created the Earldom of Lancaster—from which the house was named—for his second son Edmund Crouchback in 1267. Edmund had already been created Earl of Leicester in 1265 and was granted the lands and privileges of Simon de Montfort, 6th Earl of Leicester, after de Montfort's death and attainder at the end of the Second Barons' War. When Edmund's son Thomas, 2nd Earl of Lancaster, inherited his father-in-law's estates and title of Earl of Lincoln he became at a stroke the most powerful nobleman in England, with lands throughout the kingdom and the ability to raise vast private armies to wield power at national and local levels. This brought him—and Henry, his younger brother—into conflict with their cousin King Edward II, leading to Thomas's execution. Henry inherited Thomas's titles and he and his son, who was also called Henry, gave loyal service to Edward's son King Edward III.

The second house of Lancaster was descended from John of Gaunt, a Plantagenet prince, who married the heiress of the first house, Blanche of Lancaster. Edward III married all his sons to wealthy English heiresses rather than following his predecessors' practice of finding continental political marriages for royal princes. Henry of Grosmont, 1st Duke of Lancaster, had no male heir so Edward married his son John to Henry's heiress daughter and John's third cousin Blanche of Lancaster. This gave John the vast wealth of the House of Lancaster. Their son Henry usurped the throne in 1399, creating one of the factions in the Wars of the Roses. There was an intermittent dynastic struggle between the descendants of Edward III. In these wars, the term "Lancastrian" became a reference to members of the family and their supporters. The family provided England with three kings: Henry IV (r. 1399–1413), Henry V (r. 1413–1422), and Henry VI (r. 1422–1461 and 1470–1471).

Edward II (25 April 1284 – 21 September 1327), also known as Edward of Caernarfon or Caernarvon, was King of England from 1307 until he was deposed in January 1327. The fourth son of Edward I, Edward became the heir to the throne following the death of his older brother Alphonso. Beginning in 1300, Edward accompanied his father on campaigns in Scotland, and in 1306 he was knighted in a grand ceremony at Westminster Abbey. Edward succeeded to the throne the next year, following his father's death. In 1308, he married Isabella, daughter of the powerful King Philip IV of France, as part of a long-running effort to resolve the tensions between the English and French crowns.

Edward had a close and controversial relationship with Piers Gaveston, who had joined his household in 1300. The precise nature of Edward and Gaveston's relationship is uncertain; they may have been friends, lovers, or sworn brothers. Gaveston's arrogance and power as Edward's favourite provoked discontent both among the barons and the French royal family, and Edward was forced to exile him. On Gaveston's return, the barons pressured the King into agreeing to wide-ranging reforms called the Ordinances of 1311. The newly empowered barons banished Gaveston, to which Edward responded by revoking the reforms and recalling his favourite. Led by Edward's cousin Thomas, 2nd Earl of Lancaster, a group of the barons seized and executed Gaveston in 1312, beginning several years of armed confrontation. English forces were pushed back in Scotland, where Edward was decisively defeated by Robert the Bruce at the Battle of Bannockburn in 1314. Widespread famine followed, and criticism of the King's reign mounted.

The Battle of Burton Bridge was fought between Thomas, 2nd Earl of Lancaster and his cousin King Edward II of England during the Despenser War, from 7 to 10 March 1322. Edward's army was proceeding northwards to engage Lancaster, having defeated his Marcher Lord allies in Wales. Lancaster fortified the bridge at Burton upon Trent, an important crossing of the River Trent, in an attempt to prevent the King from proceeding. Edward arrived at nearby Cauldwell on 7 March 1322 and intended to use the ford at Walton-on-Trent to cross the river and outflank Lancaster. Edward was delayed for three days by floodwaters, during which time some of his force was deployed opposite Lancaster's men at the bridge.

On 10 March 1322 Edward's main force crossed the river at Walton and proceeded to the south side of Burton. Lancaster moved his men outside the town, intending to face the King in open battle, but withdrew northwards when he saw that he was heavily outnumbered. Lancaster was pursued closely by the King's men and eventually captured at the Battle of Boroughbridge; he was later executed on the King's orders. Lancaster's defeat removed the immediate threat to Edward's rule, but the King continued to prove unpopular with his barons, and in 1327 was forced to abdicate the throne in favour of his son Edward III.