 During this time he was resident at Trerose in the nearby parish of Mawnan.In February 1639 Slanning embarked with 13 guns and 100 officers bound for Cumberland to take part in the abortive First Bishops' War.It is possible that the men and guns were intended for the defence of Carlisle, but Slanning headed for York to command a company in a regiment of foot "appointed to guard the king's person", with the rank of Sergeant Major.