The latter did not venture their ships-of-the-line in its narrow waters, and expeditions intending to land were directed upon the ocean ports in the south and west.

At the supreme moment the great French fleet was sent upon the south coast of England, where it decisively defeated the allies, and at the same time twenty-five frigates were sent to St.George's Channel, against the English communications.

In the midst of a hostile people, the English army in Ireland was seriously imperilled, but was saved by the battle of the Boyne and the flight of James II.
This movement against the enemy's communications was strictly strategic, and would be just as dangerous to England now as in 1690.
Spain, in the same century, afforded an impressive lesson of the weakness caused by such separation when the parts are not knit together by a strong sea power.

She then still retained, as remnants of her past greatness, the Netherlands (now Belgium), Sicily, and other Italian possessions, not to speak of her vast colonies in the New World.

Yet so low had the Spanish sea power fallen, that a well-informed and sober-minded Hollander of the day could claim that "in Spain all the coast is navigated by a few Dutch ships; and since the peace of 1648 their ships and seamen are so few that they have publicly begun to hire our ships to sail to the Indies, whereas they were formerly careful to exclude all foreigners from there....