Several comparatively stable Tudor reigns had allowed England to build manufacturing and military capacity even before it became a major power. Workshops and supply systems could produce cannon, muskets, ships, and trained personnel for a sustained defense. Its geography forced Spain into a difficult amphibious operation because an army could not simply march across a land frontier. The English fleet combined royal ships with armed merchant or privateering vessels and already possessed experience, supplies, and a working command structure.
Chapter · 9:14-16:40
Why England mattered as a Protestant island base
Political stability, growing military production, and the Channel made England a useful Protestant power that Spain could not defeat by marching overland.