He fought at the Battle of Blore Heath and was captured and imprisoned by the Lancastrians. After the Yorkist victory at Northampton he was released, but was captured again at the Second Battle of St Albans.
In reward for driving out the Lancastrians, Montagu was created Earl of Northumberland. This title had long been held by the Percy family, but they were in disgrace. However, when Henry Percy was rehabilitated in 1470, Montagu was forced to give up the earldom and many important offices in favour of his former foe.
He was in compensation created Marquess of Montagu, but without suitable estates to support such a dignity. Now set against Edward IV, he joined his brother Warwick the Kingmaker in the restoration of Henry VI. Montagu returned to high office in the north, but was killed at the Battle of Barnet.
He married Isabel Ingoldsthorpe (1441-1476) and had seven children:
Lucy Neville was the Ancestor of President Franklin Roosevelt and Sir Winston Churchill.
Isabel married a year after his death, to Sir William Norreys.
A full account of the life of John Neville, 1st Marguess of Montagu, is given in Lady of the Roses A Novel of the Wars of the Roses, Penguin Group, (January 2008) by Sandra Worth. ISBN-10: 0425219143 This historically accurate novel represents the first fictional exploration of the Kingmaker's brother, and gives the Neville point of view through the events of the period of history 1455-1475, as narrated by his wife Isobel Ingoldesthorpe.