During this summer, Oliver had not only been gloriously engaged at sea, but he had been busy on land. He was in league with Louis XIV. of France to drive the Spaniards from the Netherlands. The French forces were conducted by the celebrated Marshal Turenne, and the Spanish by Don John of Austria, and the French insurgent chief, the Prince of Condé. Cromwell sent over six thousand men under Sir John Reynolds, who landed near Boulogne on the 13th and 14th of May. They were supported by a strong fleet under Admiral Montague, the late colleague of Blake, which cruised on the coast. The first united operations were to be the reduction of Gravelines, Mardyke, and Dunkirk, the first of which places, when taken, was to belong to France, the two latter to England. If Gravelines were taken first, it was to be put into possession of England, as a pledge for the conveyance of the two latter. This bold demand on the part of Cromwell astonished his French allies, and was violently opposed by the French cabinets, who told Louis that Dunkirk once in the hands of the English, would prove another Calais to France. But without Dunkirk, which Cromwell deemed necessary as a check to the Royalist invasions from the Netherlands, with which he was continually threatened, no aid was to be had from the Protector, and it was conceded, whence came the angry declaration from the French, that "Mazarin feared Cromwell more than the Devil." The French Court endeavoured to employ the English forces on other work than the reduction of these stipulated places. The young French king went down to the coast to see the British army, and having expressed much admiration of them recommended them to lay siege to Montmédy, Cambray, and other towns in the interior. Cromwell was, however, too much of a man of business and a general to suffer this. He ordered his ambassador, Sir William Lockhart (who had married the Protector's niece, Miss Rosina Sewster) to remonstrate, and insist on the attack of Gravelines, Mardyke, and Dunkirk. He told the ambassador that to talk of Cambray and interior towns as guarantees was "parcels of words for children. If they will give us garrisons, let them give us Calais, Dieppe, and Boulogne." He bade him tell the Cardinal that if he meant any good from the treaty with him, he must keep it, and go to work on Dunkirk, when, if necessary, he would send over two thousand more of his veterans. This had the necessary effect: Mardyke was taken after a siege of three days only, and put into the hands of the English on the 23rd of September. The attack was then turned on Gravelines; but the enemy opened their sluices, and laid all the country round under water. On this Turenne, probably glad of the delay, put his troops at that early period into winter quarters. During this time attempts were made to corrupt the English officers by the Stuart party. The Duke of York was in the Spanish army with the English Royalist exiles,