Erpingham crossed over from England to Normandy with Henry's army on 11 August 1415. The King's ship reached the mouth of the River Seine on 13 August, and the army landed from Harfleur, a landing point likely to have been decided on beforehand. Erpingham's men were present during the siege of the town, and on 22 September he led the procession to the walls and presided over the truce that led to its surrender. The English army then marched towards Calais, shadowed by the French, who forced them to divert away from the coast. The English successfully forded the River Somme at Voyennes; two days' march short of Calais, they were blocked by the French near Agincourt.