In July 1415 he enlisted with Thomas Fitzalan, 12th Earl of Arundel to take part in Henry 's first expedition to France. Arundel's force consisted of 100 men-at-arms and 300 mounted archers, including the Corbet brothers. The Siege of Harfleur brought a devastating outbreak of dysentery, which was the main cause of death and invalidity in his retinue. A quarter of the force were casualties of the siege. Both Burley and Arundel were invalided home and did not take part in the Agincourt campaign. Arundel returned to England on 28 September to recuperate at Arundel Castle, attended by William Burley, but died there on 13 October. Burley returned to England on 4 October.