The Percy family were one of the major defenders of the North of England against invasion by the Scots. They had centuries-long service under the English Monarchy but were not afraid to express dissent when they thought the King was acting unfairly. Given their importance for the security of the realm they had to be listened to but also sometimes put back in their place. One such time was at the Battle of Shrewsbury (1403) when the heir to the earldom, Henry ‘Hotspur’, was killed after disputing several of Henry IV ‘s decisions which he thought diminished the power and honour of the Percy family. So the earldom skipped a generation.
The Earldom was then removed from the Percys and given to John Neville, the younger brother of Warwick the ‘Kingmaker’. After a dozen years of petitioning and promising loyalty to Edward IV, the earldom was transferred back to Henry Percy as 4th earl and he was given high offices in the second reign of Edward but downgraded somewhat in Richard III’s government in an attempt to spread the power of noble families more widely. This presumably caused some resentment in the mind of Percy.
At Bosworth he commanded the rear guard but never engaged in the battle.
After Bosworth, he was imprisoned on a charge of treason but managed to persuade Henry VII that he would be a loyal subject, was released and his lands and titles restored.