 In 1294 the French king declared the English duchy of Aquitaine forfeit , and war broke out between the two countries . Edward I embarked on a wide @-@ scale and costly project of building alliances with other princes on the Continent , and preparing an invasion . When the king , at the parliament of March 1297 in Salisbury , demanded military service from his earls , Roger Bigod , Earl of Norfolk , refused in his capacity of marshal of England . The argument was that the king 's subjects were not obliged to serve abroad if not in the company of the king , but Edward insisted on taking his army to Flanders while sending his earls to Gascony . 
