Edmund fought in several expeditions against the French. He was Chief Commissioner for the defense of the Kentish coast against the French on 30 June 1377. He fought in the expedition against St. Malo in 1378. He was Chief Commissioner to treat with the ambassador of Bohemia concerning the King's marriage on 29 March 1381. He fought in the expedition in Portugal against the Spaniards in 1382, which he commanded without much success. He was created 1st Duke of York [England] on 6 August 1385. He held the office of Justice of Chester and county Flint on 28 September 1385. He was a member of the Council of Regency on 19 November 1386. He held the office of Keeper of the Bailiwick of the Forests of Rutland and Leighfield on 4 May 1388. He was Commissioner to treat for peace with France on 10 March 1394, along with Lancaster. He was Surveyor of the temporalities of the Archbishop of Canterbury on 5 August 1396. He held the office of Keeper of Mortagne-sur-la-Gironde on 24 February 1397. He held the office of Keeper of Freemantle Park, Hampshire on 12 May 1397. He held the office of Steward of England between 20 March 1399 and August 1399. On 27 July 1399 at Berkeley, Gloucestershire, England, he made his peace with the new King Henry IV, instead of opposing his landing.
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