The Duke of York, head of the Yorkist party, is the Richard Plantagenet of Henry VI, Part One, an English nobleman convinced that his claim to the throne is better than King Henry’s.
He is a proud and ambitious man who aims to make himself King, and is ready to take actions he knows to be of questionable morality to do so. He joins in the plot against the Duchess of Gloucester, is a prime mover of the coup that overthrows Gloucester himself, and he urges Cade to rebel for the sake of seeing what popular opinion will think of a challenge to Henry’s rule and providing an excuse to bring his army home, no matter the cost to the country. Leaving aside the question of Henry’s right to the throne, York despises him as being unfit to wear the crown. He has an ongoing feud with Somerset and Suffolk, but joins with the latter to plot Gloucester’s death. Sent to Ireland to put down a rebellion, he leaps at the chance to raise an army, and having subdued the Irish uses it to push his claims in England. Though he attempts to present himself as a loyal subject for as long as possible, the longer he spends as a mere subject the more enraged he grows, and seeing Somerset at liberty after being told he had been imprisoned proves the final straw, and he openly announces his rebellion, despite having only the Nevilles (Salisbury and Warwick) on his side, along with his sons Edward and Richard. His revolt leads to the battle of Saint Albans, which he wins; the rest of his career can be found in Henry VI, Part Three.