in the rear. The Dutch van was commanded by Tromp, the centre by Lieutenant-Admiral Aert Jansse van Nes under direct supervision of De Ruyter himself and the rear by Lieutenant-Admiral Adriaen Banckert. Rupert, convinced that the smaller Dutch fleet would withdraw to Hellevoetsluis when pressed, detached a special squadron at nine in the morning to cut off the retreating Dutch from the north. In this taskforce he concentrated all lighter ships from the regular squadrons so that it would be able to manoeuvre more easily over the shoals. However, De Ruyter did not budge. When however the squadron at last returned to the main allied line, joining Rupert's squadron, the Dutch started to move, but surprisingly in the direction of the enemy. This forced Rupert to attack immediately to prevent the Dutch from gaining the weather gauge, before he could form a proper keel line. The battle began at noon and lasted for nine hours. Using his superior knowledge of the shallow waters, De Ruyter was able to manoeuvre his fleet so close to the shoals that the allies found it difficult to engage without grounding. Rupert first made contact with the squadron of Cornelis Tromp. He had now about half of the allied fleet with him. Sailing slowly to the northeast after some time he reached the edge of the basin. This gave him the opportunity to surround Tromp from the north with the mass of frigates while simultaneously using his favourable windward position to attack him directly from the west with the heavy English ships. The frigate squadron was now in complete disarray however and could not execute such a complicated manoeuvre. Nor did Rupert choose the direct attack. He was much criticised for this afterwards and defended himself by claiming his approach would have been blocked by shoals. This was simply not true and Rupert knew it. Whatever his motives he turned to the southwest, both fleets bombarding each other from a distance, the Dutch inferiority in numbers compensated by the fact that their leeward position gave their guns a better range and the lack of a proper battle line in the enemy squadron. De Ruyter had at first closely followed Tromp; but becoming aware the French flotilla of de Grancey had joined Spragge against Banckert, creating a gap in the French line, he suddenly tacked to the southwest, separating Tromp from the rest of the Dutch