Margaret was important in the Wars of the Roses. At times, she personally led the House of Lancaster into battle. Her husband had several nervous breakdowns. They were seen as insanity, so Margaret ruled the kingdom in his place. It was she who called for a Great Council in May 1455 that excluded the House of York headed by Richard of York, 3rd Duke of York. This started a civil conflict that lasted for more than thirty years. This conflict caused the deaths of thousands of men. One of those who died was her only son Edward of Westminster, Prince of Wales, at the Battle of Tewkesbury in 1471.