In the following years Montagu served the king in various capacities, primarily in the Scottish Wars. He was richly rewarded, and among other things received the lordship of the Isle of Man. In 1337, he was created Earl of Salisbury, and given an annual income of 1000 marks to go with the title. He served on the Continent in the early years of the Hundred Years' War, but in 1340 he was captured by the French, and in return for his freedom had to promise never to fight in France again. Salisbury died of wounds suffered at a tournament early in 1344.