During the years preceding the war the Dutch made every diplomatic effort to avert it, but the hatred of Charles and Louis prevented any concession being accepted as final. An English royal yacht was ordered to pass through the Dutch ships-of-war in the Channel, and to fire on them if they did not strike their flags. In January, 1672, England sent an ultimatum, summoning Holland to acknowledge the right of the English crown to the sovereignty of the British seas, and to order its fleets to lower their flags to the smallest English man-of-war; and demands such as these received the support of a French king. The Dutch continued to yield, but seeing at length that all concessions were useless, they in February ordered into commission seventy-five ships-of-the-line, besides smaller vessels. On the 23d of March the English, without declaration of war, attacked a fleet of Dutch merchantmen; and on the 29th the king declared war. This was followed, April 6th, by the declaration of Louis XIV.; and on the 28th of the same month he set out to take command in person of his army. The war which now began, including the third and last of the great contests between the English and Dutch upon the ocean, was not, like those before it, purely a sea war; and it will be necessary to mention its leading outlines on the land also, not only in order to clearness of impression, but also to bring out the desperate straits to which the republic was reduced, and the final deliverance through its sea power in the hands of the great seaman De Ruyter.