What wrecked it as a military force was the revolution which was taking place in the art of war.

The introduction of gunpowder ruined feudalism.

The mounted and heavily-armed knight gave way to the meaner footman.

Fortresses which had been impregnable against the attacks of the Middle Ages crumbled before the new artillery.

Although gunpowder had been in use as early as Crecy, it was not till the accession of the House of Lancaster that it was really brought into effective employment as a military resource.