The Treaty of Paris signed in March 1657 allied the English Protectorate of Oliver Cromwell with King Louis XIV of France against King Philip IV of Spain, merging the Anglo-Spanish War (1654–1660) with the larger Franco-Spanish War (1635-1659). The treaty confirmed the growing rapprochement between France and the English Republican regime. Until the mid-1650s the French had been supporters of the Royalist exiles under Charles II, but the move towards an alliance with Cromwell led Charles to conclude the Treaty of Brussels with Spain in 1656.
Terms
Based on the terms of the treaty, the English would join with France in her continuing war against Spain in Flanders. France would contribute an army of 20,000 men, England would contribute both 6,000 troops and the English fleet in a campaign against the Flemish coastal fortresses of Gravelines, Dunkirk and Mardyck. It was agreed that Gravelines would be ceded to France, Dunkirk and Mardyck to England. Dunkirk, in particular, was on the Commonwealth's mind mainly because of the privateers that were causing damage to the mercantile fleet. For Cromwell and the Commonwealth, the question of possession of Dunkirk thus passed from regional diplomatic possibility to urgent political necessity.