Rooke stopped intercourse between Ireland and Scotland, where were many Stuart partisans, and then with his small squadron passed along the east coast of Ireland, attempted to burn the shipping in Dublin harbor, failing only through lack of wind, and finally came off Cork, then occupied by James, took possession of an island in the harbor, and returned in safety to the Downs in October.

These services, which raised the siege of Londonderry and kept open the communications between England and Ireland, extended throughout the summer months; nor was any attempt made by the French to stop them.

There can be little doubt that an effective co-operation of the French fleet in the summer of 1689 would have broken down all opposition to James in Ireland, by isolating that country from England, with corresponding injury to William's power.
The following year the same strategic and political mistake was made.
It is the nature of an enterprise such as James's, dependent upon a weaker people and foreign help, to lose strength if it does not progress; but the chances were still in his favor, provided France co-operated heartily, and above all, with her fleet.

It is equally the nature of a merely military navy like that of France to be strongest at the beginning of hostilities; whereas that of the allied sea powers grew daily stronger, drawing upon the vast resources of their merchant shipping and their wealth.

The disparity of force was still in favor of France in 1690, but it was not as great as the year before.