The siege of Norham (June-July 1463) was the most active Scottish intervention in the fighting in Northumberland in 1461-64 but ended as an embarrassing fiasco after the Lancastrian-Scottish army fled in the face of a Yorkist relief force.
In the aftermath of the battle of Towton the castles of Dunstanburgh, Alnwick and Bamburgh were all held by Lancastrian supporters, but over the next few years they frequently changed hands. In March 1463 all three were handed over the Lancastrians - Sir Ralph Grey surrendered Alnwick while Sir Ralph Percy handed over Bamburgh and Dunstanburgh. By this point the Lancastrians, who were effectively led by Queen Margaret, could count on Scottish support. Power in Scotland was mainly in the hands of the regent, Queen Mary of Gueldres, the mother of the twelve-year old James III. Queen Margaret had also visited France and returned with a force of French troops under Pierre de Brézé.
In late June or early July 1463 the Scots made their biggest effort to support the Lancastrians. A combined Scottish and Lancastrian army, which included Queen Mary, the young James III, Queen Margaret and Henry VI and Brézes, laid siege to Norham Castle, an important English border castle to the west of Berwick.
The earl of Warwick and his brother John Neville Lord Montagu, responded by gathering an army and advancing towards Norham. They arrived in July, eighteen days after the start of the siege. The Scottish-Lancastrian army fled in panic. Queen Margaret and her son escaped to Berwick, from where they sailed to the continent. Henry VI remained in Scotland, where he was protected by Bishop Kennedy of St. Andrews. Henry and Margaret would never meet again.
The Nevilles raided southern Scotland, reaching sixty-three miles across the border before a lack of supplies forced them to retire. This embarrassing failure greatly reduced Scottish enthusiasm for the war. With Queen Margaret and Brézé gone, Queen Mary negotiated a ten month truce which began in December 1463. The effective Scottish contribution to the Lancastrian cause was over.