The Wars of the Roses lasted 32 years, from 1455 to 1487. The conflict began with the First Battle of St Albans, when Yorkist forces defeated and captured the Lancastrian king, Henry VI. It ended after Henry Tudor defeated Richard III at the Battle of Bosworth Field in 1485 and secured his position through the defeat of the Yorkist pretender Lambert Simnel at the Battle of Stoke Field in 1487.
The wars were a series of civil conflicts between supporters of the rival houses of Lancaster and York, both branches of the Plantagenet royal family. They were driven by disputes over succession, noble rivalries, weak royal government and the political fallout from the Hundred Years' War.
The 32-year figure is a straightforward calculation: 1487 minus 1455 equals 32. However, fighting was not continuous throughout that period. There were long pauses, changing alliances and several distinct campaigns. The name “Wars of the Roses” was also coined later; contemporaries more often referred to the struggles as the civil wars or the Cousins' War.