The capture of Sandwich (June 1460) was a key Yorkist success that allowed the exiled earls of Salisbury, Warwick and March to invade England from their base at Calais at the start of the campaign that ended with the great Yorkist victory at Northampton.
In 1459 the Lancastrians had decided to move against the Yorkists and had charged Richard Neville, earl of Salisbury, Richard Neville, earl of Warwick and Richard, earl of York, with treason. Unlike in 1455 the court also made military preparations, and so when the Yorkists raised an army they were outnumbered. At Ludford Bridge (12-13 October 1459) the senior Yorkist commanders, realising that they were outnumbered, decided to flee, abandoning their army. York escaped to Ireland, while Salisbury, Warwick and York's Edward earl of March (the future Edward IV) escaped to Calais. This was Warwick's military power base, although the desertion of part of the Calais garrison at Ludford Bridge had played a part in the Yorkist collapse.
Over the next few months most of the fighting was concentrated around Calais and Sandwich. Henry Beaufort, duke of Somerset, the son of the duke of Somerset killed at the First Battle of St. Albans, was sent to take Calais. He was unable to take the port but did establish himself at the outlying castle of Guines. A Lancastrian fleet was gathered at Sandwich, but on 15 January 1460 a Yorkist force under John Dinham captured this fleet, along with Richard Woodville, Earl Rivers, the commander of the garrison. After this success Warwick sailed for Ireland, where he met with York and the two men came up with a plan for a two-pronged invasion of England. A Lancastrian fleet failed to intercept Warwick as he returned to Calais, and the plan was soon put into effect.
Early in June 1460 Sandwich was defended by a force of 200 archers and 200 men-at-arms, commanded by Sir Osbert Mountfort. This force was preparing to cross the channel to join Somerset at Guines.
The attacking force was led by William Neville Lord Fauconberg, John Wenlock and John Dinham. Their force crossed to Sandwich early in June and after some hard fighting captured the town. Mountfort was taken back to Calais where as a loyal support of Somerset he was executed. Fauconberg remained in Sandwich with most of the Yorkist raiding party. On 26 June he was joined by Warwick, Salisbury and March with around 2,000 men. This small Yorkist force gained strength as it passed through Kent. They were admitted into London, where the Lancastrian commanders retreated into the Tower of London, and then continued north. On 10 July 1460 the outnumbered Lancastrians were defeated at the battle of Northampton. Several important Lancastrian leaders were killed and Henry VI was captured. For the moment the Yorkists appeared to be in the ascendency.