The Battle of Bosworth Field was the last significant battle of the Wars of the Roses, the civil war between the Houses of Lancaster and York that raged across England in the latter half of the 15th century. Fought on 22 August 1485, the battle was won by the Lancastrians. Their leader Henry Tudor, Earl of Richmond, by his victory became the first English monarch of the Tudor dynasty. **Ancestors fought in this battle**
A stained glass window in St. James Church commemorates the Battle of Bosworth Field where Richard III's forces of 10,000 met with Henry Tudor's forces of 5,000. Due to the Stanleys, who did some fence sitting with their forces of 6,000, the battle swayed nicely in Henry's direction, making him Henry VII.
From Shadow of Night, chapter 18: "'I'm not going into Hubbard's den and arguing the geography of the city with him again', Gallowglass said, slapping his gloves against his thigh. 'He didn't agree when you made this argument so you could station the brotherhood in the Tower after we arrived to help the Lancastrians in 1485, and he's not going to agree to it now.'".
Treachery: what really brought down Richard III at the Battle of Bosworth | History Extra