After the outbreak of the Fourth Anglo-Dutch War in December 1780 the Dutch Republic became informally involved in the American Revolutionary War on the side of France and its allies, without, however, a formal alliance being formed. On the initiative of the Amsterdam delegation in the States of Holland the States General resolved in early 1782 to come to some kind of arrangement with France to at least discuss a common strategy in the sea war, which became known as the "Concert". This proposition was accepted by the French with some alacrity, as in their eyes the Dutch military resources, especially the Dutch fleet, lay fallow in the roadstead of the Texel. When in September 1782 a large British fleet under Admiral Howe departed for besieged Gibraltar in an effort to relieve that stronghold, thereby denuding the English Channel of Royal Navy forces, the French marquis de Castries saw a chance to kill two birds with one stone, and wrote a memorandum for the French minister of foreign affairs, Vergennes, in which he proposed that the Dutch should take this opportunity to safely pass through the English Channel to send a flotilla of ships of the line to the French naval base of Brest, to use that as a permanent base for both its own operations in the Dutch East Indies (where the flotilla might turn the balance of military power in that theater of the war against the British, in combination with French naval units), and for combined naval operations with French and Spanish fleets in the area of the English Channel, to obtain a naval superiority there.