Passage: Edward and Warwick marched north, gathering a large army as they went, and met an equally impressive Lancastrian army at Towton. The Battle of Towton, near York, was the biggest battle of the Wars of the Roses. Both sides agreed beforehand that the issue would be settled that day, with no quarter asked or given. An estimated 40,000–80,000 men took part, with over 20,000 men being killed during (and after) the battle, an enormous number for the time and the greatest recorded single day's loss of life on English soil. Edward and his army won a decisive victory, and the Lancastrians were routed, with most of their leaders slain. Henry and Margaret, who were waiting in York with their son Edward, fled north when they heard the outcome. Many of the surviving Lancastrian nobles switched allegiance to King Edward, and those who did not were driven back to the northern border areas and a few castles in Wales. Edward advanced to take York, where he replaced the rotting heads of his father, his brother, and Salisbury with those of defeated Lancastrian lords such as the notorious John Clifford, 9th Baron de Clifford of Skipton-Craven, who was blamed for the execution of Edward's brother Edmund, Earl of Rutland, after the Battle of Wakefield.

Question: how many men were slayed in the Battle of Towton?
20,000 men