The siege of Alnwick (December 1462-6 January 1463) saw the castle captured by the Yorkists, although only after a Lancastrian and Scottish relief army had rescued the garrison.
Alnwick changed hands repeatedly between 1461 and 1464. After the battle of Towton it was held by the Lancastrians, as were Bamburgh and Dunstanburgh. The earl of Warwick was given the task of capturing these castles, and in September 1461 Alnwick surrendered to him. This success would be short-lived, and in November the castle fell to a Lancastrian force under Sir William Tailboys. It remained in Lancastrian hands until the summer of 1462 when under the cover of a truce with Scotland the Yorkists were able to besiege it. This siege of Alnwick (July 1462) was led by William Hastings, Lord Hastings and Sir John Howard, and ended with the surrender of the castle.
A garrison was left in Alnwick, but Yorkist control would be short-lived. In October 1462 Queen Margaret landed on the Northumbrian coast with a force of French mercenaries commanded by Pierre de Brézé. Alnwick surrendered to Queen Margaret and Robert Hungerford, Lord Hungerford was placed in command of the garrison.
Edward IV responded to this threat by sending the earl of Warwick north with a powerful army. In December 1462 he began sieges of Alnwick, Dunstanburgh and Bamburgh. William Neville, earl of Kent, Anthony Woodville, Lord Scales and John Tiptoft, earl of Worcester were given command of the siege of Alnwick.
Dunstanburgh and Bamburgh both surrendered late in December 1462, but Alnwick held out. Warwick had gunpower artillery at his disposal, but Edward chose not to use it, either because he wanted to capture the castle intact or to send a message to the garrison that he would accept their surrender on terms. At this stage Edward was willing to attempt reconciliations with many of his enemies, and after Somerset surrendered at Bamburgh he submitted to Edward and even took an active part in the remaining part of the siege of Alnwick.
The biggest threat now was a relief army that was led by de Brézé and the earl of Angus. This army reached Alnwick on 5 January 1463, and a rather farcical standoff followed. According to Warkworth's Chronicle Warwick's men were afraid of the Franco-Scottish army, and withdrew from the siege. The Scots believed that this was some sort of trap didn’t attempt to push their advantage. The garrison, under Robert Hungerford, Lord Hungerford, was able to withdraw into Scotland. A token force was left behind but this surrendered on 6 January 1463.
Alnwick didn’t remain in Yorkist hands for long. In March 1463 the Yorkist commander, Sir Ralph Grey, defected to the Lancastrians and allowed Hungerford back into the castle. Alnwick remained in Lancastrian hands for the next year. Late in 1463 Somerset changed sides yet again, and returned to Henry VI. After a successful campaign in Northumberland he was defeated twice by Montagu, at Hedgeley Moor in April and at Hexham in May. After the second battle Somerset was captured and executed. With the Lancastrian field army destroyed the garrison of Alnwick surrendered to Warwick on 23 June 1464.