 In 1542 and 1544, Thynne was with Seymour on military expeditions to the north.He was probably at the Battle of Solway Moss in 1542 and was knighted after the victory of the Battle of Pinkie Cleugh of 1547.Also in 1547, Thynne became a freeman of the City of London and a member of the Worshipful Company of Mercers.