Edward had been forced into the struggle against his will by the ceaseless attacks of France, and his claim of the crown was little but an afterthought to secure the alliance of Flanders.

The war of Henry on the other hand, though in form a mere renewal of the earlier struggle on the close of the truce made by Richard the Second, was in fact an aggression on the part of a nation tempted by the helplessness of its opponent and galled by the memory of former defeat.

Its one excuse lay in the attacks which France for the past fifteen years had directed against the Lancastrian throne, its encouragement of every enemy without and of every traitor within.
Henry may fairly have regarded such a ceaseless hostility, continued even through years of weakness, as forcing him in sheer self-defence to secure his realm against the weightier attack which might be looked for, should France recover her strength.
[Sidenote: Agincourt] In the summer of 1415 the king prepared to sail from Southampton, when a plot reminded him of the insecurity of his throne.

The Earl of March was faithful: but he was childless, and his claim would pass at his death through a sister who had wedded the Earl of Cambridge, a son of the Duke of York, to her child Richard, the Duke who was to play so great a part in the War of the Roses.

It was to secure his boy's claims that the Earl of Cambridge seized on the king's departure to conspire with Lord Scrope and Sir Thomas Grey to proclaim the Earl of March king.