Sadler was replaced by William Paget as Secretary of State in April 1543, owing to his frequent absences on diplomatic missions, but was appointed Master of the Great Wardrobe. He was treasurer for the war against Scotland with the Earl of Hertford during his punitive expedition to Edinburgh in May 1544. Sadler accompanied Hertford into Scotland, in the same role in September 1545. He accompanied Lord Hertford again, this time at the Battle of Pinkie in the post of High Treasurer of the Army. On 10 September 1547, in recognition of his services during the fighting, Sadler was made a knight banneret.