Which earl changed sides from Edward IV to Henry VI in 1470?

The earl who changed sides from Edward IV to Henry VI in 1470 was the Earl of Warwick.

Richard Neville, 16th Earl of Warwick—later famous as “Warwick the Kingmaker”—helped place Edward IV on the throne in 1461. Their relationship deteriorated over Edward’s secret marriage to Elizabeth Woodville, foreign policy, and Warwick’s loss of influence at court.

After a failed rebellion and an alliance with Edward’s brother, George, Duke of Clarence, Warwick fled to France. Louis XI helped reconcile him with Margaret of Anjou, Henry VI’s queen. Warwick then returned to England with Lancastrian support, forcing Edward IV into exile in October 1470 and restoring Henry VI.

The restoration was brief. Edward returned with Burgundian assistance in 1471, and Warwick was defeated and killed at the Battle of Barnet on 14 April. A common mix-up is confusing Warwick with the Earl of Oxford, another major Lancastrian commander who fought for Henry VI and later Henry VII.