Hoping to get England under his thumb he befriended James II, the last Stuart king, whom the English drove out in 1688. James, less bad but less clever than his vile brother Charles, had a party called Jacobites, who wanted French help to set him on the throne again, but no French interference afterwards. Most of Great Britain favoured the new king, William III; most of Ireland the old one, James. This greatly endangered British sea-power; for the French fleet had been growing very strong, and an enemy fleet based on Ireland would threaten every harbour in Great Britain from Bristol to the Clyde. More than this, a strong enough fleet could close the Channel between the south of Ireland and the north of France. There would then be no way out of Great Britain on to the Seven Seas except round the north of Scotland. But an enemy fleet strong enough to shut off Great Britain from the short cuts north and south of Ireland would certainly be strong enough to command the roundabout way as well; for it would be close to its base on the west coast of Ireland, while ships coming round by the north of Scotland would be far from their own. Thus Ireland, then as now, was the key to the sea-door of Great Britain. Luckily for Great Britain then, and for our Empire and Allies throughout the Great War, keys are no good unless you have the hand to turn them. And, then as now, the strong right hand that holds the key of Ireland was and is the Royal Navy.
In 1689 William III had at last succeeded in forming the Grand Alliance against Louis XIV, who now had enemies all round him except in little Switzerland. But France was easily the strongest of all the Great Powers, and she was under a single command; while Spain and Austria were lukewarm and weak against her, the many little German countries could not act well together, and Great Britain had many Jacobites at home besides still more in Ireland. Thus the Dutch and British friends of King William were the only ones to be depended on through thick and thin.
Moreover, the Navy had grown dangerously weak under the last two Stuart kings; and some of its men were Jacobites who knew the French king wished to put the Stuarts on the British throne again. So, when the great French admiral, Tourville, defeated the Dutch and British fleets off Beachy Head in 1690, the British fought far more feebly than the Dutch, who did as well as the best of them had done when led by the immortal van Tromp. Luckily for the British, Louis XIV did not want to make them hate him more than he could help, because he hoped to use them for his own ends when he had brought them under James again. Better still, William beat James in Ireland about the same time. Best of all, the Royal Navy began to renew its strength; while it made up its mind to stop foreign invasions of every kind. Even Jacobite officers swore they would stop the French fleet, even if James himself was on board of it. Then the tide of fortune turned for good and all.