Walter was born in 1292. He was the son of James Stewart, 5th High Steward of Scotland and Gilles (or "Egidia") de Burgh. Walter was one of the Scottish leaders at the Battle of Bannockburn. Just before the battle began Walter along with his cousin James Douglas, Lord of Douglas were knighted by King Robert the Brucealong with many others. Both he and James Douglas were both leaders of the left battalion in the battle. He took part of all the Wars of Scottish Independence between Robert the Bruce and Edward II of England.