the Dunkirk ships, the Santiago, were now downwind and on the receiving end of the cannonades of the remaining nine ships of the Dutch column. Tromp turned his column and went for another round on the Santiago. Oquendo, the other six Dunkirk ships and the San Juan, unable to turn upwind, fired as they could. The artillery did little damage, but Spanish musketry picked off many on the Dutch decks. This encounter lasted for three hours, in the course of which the Dutch ship Groot Christoffel accidentally exploded. By noon, the six ships of the Witte de With column had reached Tromp, and increased his number to 16. Although the rest of the Spanish fleet remained dispersed and disorganized, many units had finally turned and were also approaching from the other side. For Tromp, this was building up into a dangerous situation, as the Spanish units upwind would cut off his exit, and force the Dutch squadron to turn into the shoals of the bay of Boulogne and almost certainly run aground. However, at this moment, Oquendo ordered the Spanish fleet to resume a half-moon formation. The Spanish ships turned, allowing Tromp's squadron to turn also, gain the wind, and escape the danger. There were no more engagements that evening. The fleets anchored in, and the next day, rear-admiral Joost Banckert arrived, bringing the total Dutch fleet to thirty-two. But there was no engagement, just preparations for what was to become known as the action of 18 September 1639. The Spanish, whose priority was to protect the troops, not to endanger them by continuing the battle, took refuge in The Downs, an anchorage between the English ports of Dover and Deal, near an English squadron commanded by Vice-Admiral John Pennington. Ocquendo ordered 13 of his Dunkirker squadron, composed of light, fast frigates, to head north at night round the Goodwin Sands; although the Dutch later sealed this exit, they arrived in Dunkirk with 3,000 troops and all the bullion intended to pay the Army of Flanders. Ultimately, the Spanish calculated 6,000 troops had been landed, with 1,500 captured by the Dutch and another 1,500 either killed or interned in England, which allowed Ocquendo to later claim he had largely achieved the objectives set. On the evening of 28 September, Tromp and De With withdrew to resupply, for they were short of gunpowder. They feared they had failed in their mission