The future of the Stuart composite monarchy turned on a maritime invasion in the autumn of 1688 which brought William of Orange to the throne as William III of England and II of Scotland. It also triggered a prolonged period of war with France which would absorb three-quarters of the remaining years of the regal union, a sharp contrast with the short Dutch wars. The possibility that another maritime invasion might undo that first one hung like a sword of Damocles over the authorities on both sides of the Tweed. Thus, the royal navy as a maritime shield for Scotland acquired a new importance, but its position as a locus of the personal union was also challenged by a less maritime-minded monarch, the pressure of war, and the rising influence of both kingdoms’ parliaments.

War to the West

William briefly considered the possibility of a landing in Scotland, but ultimately he would go where the wind best suited and this proved to be west rather than north. The royal navy was windbound on the Essex coast, causing its commander, George Legge, Baron Dartmouth, ‘no little vexation’, and while the Dutch were unloading, his fleet was still two hundred miles east. With William ashore, James joined his army on Salisbury Plain, which included all the Scottish regulars as the militia made James's Scottish position appear strong; thus the army became the expeditionary force that Lauderdale and Rothes had envisaged. The king lost his nerve and fled, so on Christmas Day William was offered the crown of England; a revolution effected principally by foreign invasion rather than domestic rebellion. Nevertheless, James's regime was in trouble before William landed, and perhaps was already collapsing. That was a prerequisite for William's attempt; even having landed, the royal navy was still a serious threat, sitting across the Dutch lines of communication. Had James succeeded in confining William to the west, this would have loomed large as the land campaign lengthened. Many naval officers were of dubious loyalty to James, but the two fleets had been prevented from fighting by the winds rather than disaffection.

In Scotland James's regime evaporated; William's partisans picked up the reins with elections to the convention of the estates in March 1689.