He began his military career in August 1492 at the age of fifteen under Sir Edward Poynings at the siege of Sluys.
[2] Surrey knighted both Thomas and Edward on 30 September 1497 at Ayton Castle after the signing of a treaty concluding an invasion by James IV of Scotland.
When war with France broke out in April 1512, Howard was appointed admiral of a fleet of 18 ships sent by the King to keep the seas between Brest and the Thames estuary.
At the beginning of June, he escorted to Brittany the army which Henry was sending to France under the Marquess of Dorset with the hope of recovering Guyenne.
Howard attacked, and in the ensuing Battle of Saint-Mathieu the two largest ships on either side, the Regent and the Marie de la Cordelière, were destroyed when the latter's magazine exploded.
On 10 October the King showed his appreciation by awarding Howard an annuity of 100 marks and the reversion of the office of Lord High Admiral held by the Earl of Oxford.
The French were unable to exploit Howard's death, and after successful English campaigns in Picardy and Scotland, a truce was agreed on in March 1514.
As a younger son, he held only the manor of Morley in Norfolk, which he willed in reversion to his stepson, Henry Parker, after the termination of his widow's life interest.