How did the Stanley family affect the outcome of the Battle of Bosworth Field?

The Stanley family played a decisive role in the outcome of the Battle of Bosworth Field, effectively securing the victory for Henry Tudor.

Although Thomas, Lord Stanley—Henry’s stepfather—remained officially neutral during the engagement, his brother, Sir William Stanley, had privately pledged support to Henry. As the battle progressed and Richard III moved to attack Henry Tudor directly, Sir William Stanley intervened by attacking the Yorkist flank. This maneuver caused the Yorkist army to collapse, leading to the death of Richard III and the end of his reign.1234

Following the battle, Thomas Stanley, who had avoided direct combat, famously placed the crown on Henry’s head, signaling the rise of the Tudor dynasty. Henry VII subsequently rewarded the family by confirming Thomas in his offices and creating him the 1st earl of Derby.12