The aggressive attack on St. Domingo at once decided the hostility of Spain towards the Commonwealth, and drove her to take Cromwell's most formidable enemy, Charles Stuart, to her heart. The Protector, on his side, hastened to make treaty of peace and friendship with France, which he presently expanded into an offensive and defensive alliance. Mazarin, who had to encounter not only Spain but Condé, was only too glad to welcome the English to his side. By the terms of the treaty it was agreed that the French should provide twenty thousand men, and the English six thousand men, as well as a fleet, for the coming campaign against the Spaniards in Flanders. Of the English six thousand half were to be paid by France, but the whole were to be commanded by English officers, and reckoned to be the Lord Protector's forces. The plan of campaign was the reduction of the three coast-towns of Mardyck, Dunkirk, and Gravelines, of which the two first were to be made over to England and the third retained by France. Cromwell's great object was to secure a naval station from which he could check any attempted invasion of England by Charles Stuart from Spanish Flanders, and he was therefore urgent that Dunkirk should be first attacked. Turenne disliked this design, and even threatened to throw up his command if it should be insisted on. To beleaguer Dunkirk without first securing Nieuport, Furnes, and Bergues would, he said, be to be besieged while conducting a siege. But Cromwell had made up his mind that the thing should be done, and, as shall soon be seen, it was done. [Sidenote: 1657.] Throughout the spring of 1657 therefore preparations for the expedition kept both military and naval departments busily employed, for the fleet was not only to supply the army but to second its operations. The six thousand men, though for the most part old soldiers, were made up of drafts and of new recruits, and were distributed into six regiments. Turenne would gladly have preferred complete corps from the standing Army, but in the existing menace of invasion Cromwell was indisposed to spare them. Nevertheless the new regiments were in perfect order and discipline when they embarked on the 1st of May from Dover for Boulogne. The general in command was Sir John Reynolds, whom we saw lately in Ireland; the major-general was Thomas Morgan, Monk's right-hand man in the Highland war, an impetuous little dragoon known by the name of the "little colonel,"[188] and justly reputed to be one of the best officers in the British Isles.