Edmund received the county of Mortain in Normandy on 22 April 1427. Edmund became a commander in the English army in 1431, and in 1432 was one of the envoys to the Council of Basel. After his recapture of Harfleur and his lifting of the Burgundian siege of Calais, he was named a Knight of the Garter in 1436. After subsequent successes he was created Earl of Dorset on 28 August 1442 (though he seems to have been styled as such since around 1438) and Marquess of Dorset on 24 June 1443. During the five-year truce from 1444 to 1449 he served as Lieutenant of France. On 31 March 1448 he was created Duke of Somerset. As the title had previously been held by his brother, he is sometimes mistakenly called the second duke, but the title was actually created for the second time, and so he was actually the first duke, the numbering starting over again.