In June the two fleets, under the Duke of York and the Dutch Admiral Opdam, each numbering nearly a hundred sail, were in the North Sea, and on the 3rd they met in battle, some thirty-five miles south-east of Lowestoft. Opdam was driven back to the Texel with the loss of several ships. The Duke of York had behaved with courage and spirit during the fight, and was covered with splashes of the blood of officers killed beside him on the quarter-deck, where he himself was slightly wounded. But he showed slackness and irresolution in the pursuit, and failed to reap the full results of his victory.
During the rest of the summer there were more or less successful enterprises against Dutch trade; but the plague in London, in the ports and dockyards, and even in the fleet itself, seriously interfered with the prosecution of the war. As usual at that time, the winter months were practically a time of truce. In the spring of 1666 both parties were ready for another North Sea campaign.
The Dutch had fitted out more than eighty ships under Admiral De Ruyter, and the English fleet was put under the command of Monk, Duke of Albemarle, with Prince Rupert, the fiery cavalry leader of the Civil War, as his right-hand man. Both were soldiers who had had some sea experience. It was still the time when it was an ordinary event for a courtier to command a battleship, with a sailor to translate his orders into sea language and look after the navigation for him. Pepys tells how he heard Monk's wife, the Duchess of Albemarle (perhaps echoing what her husband had said in private), "cry mightily out against the having of gentlemen captains, with feathers and ribbons, and wish the King would send her husband to sea with the old plain sea-captains that he served with formerly."
Monk and Rupert went to join the fleet that was assembling at the Nore on 23 April. It was not ready for sea till near the end of May. On 1 June, when part of the fleet was detached under Rupert to watch the Straits of Dover, Monk met De Ruyter (who was in superior force) off the Essex coast and began a battle that lasted for four days. The news of the first day's fighting set London rejoicing, but soon there came disappointing reports of failure.
The four days' battle had ended in defeat. Outnumbered as he was, Monk had made a splendid fight on the first two days, hoping from hour to hour for Rupert's arrival. On the third day, the Sunday, he had to retire towards the Thames, covering his retreat with a rearguard of sixteen of his best ships. Several of these touched on the Galloper Sand, and Ascue's ship, the "Prince," ran hard aground on the bank. Ascue struck his flag, and the Dutch burned his ship, abandoning an effort to carry her off because at last Rupert's squadron was in sight. On the fourth day a confused mêlée of hard fighting off the Thames mouth ended in Monk retiring into the river. He had lost twenty ships and some three thousand men; but he had fought so well that the Dutch bought their victory dearly, and, after attempting for a few days to blockade the Thames, had to return to Holland to refit and make good their losses.
Amid the general discouragement at the failure of the fleet there was an outburst of mutual accusations of misconduct among the captains, and even some bitter attacks on Monk, the "General at Sea." Fault was found with the dividing of the fleet on a false report; with Monk's haste to attack the Dutch when he was short of ships; and, finally, with his retreat before the enemy into the Thames. Monk, however, did not bear himself like a beaten man. He spoke of the long battle as, at the worst, an indecisive engagement, and said he had given the Dutch as many hard knocks as he had taken, and now knew how to defeat them. He had sufficient influence at Court to be able to retain his command, and so could look forward to trying his fortune again before long.
The work of refitting the fleet was taken in hand. At any cost, the danger of a blockade of the Thames must be averted, so the merchants of the City combined to help with money, and even some of the rich men of the Court loosed their purse-strings. A fine three-decker launched at Chatham was named the "Loyal London," in compliment to the exertions of the City, and work was pushed on so rapidly that she was soon ready for commission. Many of the ships had been shorthanded in the four days' battle. The pressgangs were now set vigorously to work, and, though there was a constant drain of desertions to contend with, the numbers on board the ships at Chatham and in the lower Thames rose day by day.
At the end of June a new impetus was given to the preparations by the reappearance of De Ruyter's fleet. He had repaired damages more quickly than his opponents, and put to sea to blockade the Thames. It was on 29 June that the fishermen of Margate and Broadstairs saw a great crowd of strange sail off the North Foreland. It was the Dutch fleet of over a hundred ships, great and small, and commanded by De Ruyter, Van Tromp, and Jan Evertszoon. Some of the ships stood in close to Margate. The militia of the county was called out, and the alarm spread along the southern coast, for the rumour ran that the Dutch had come to cover a French invasion. But no Frenchmen came, and the Hollanders themselves did not send even a boat's crew ashore. They were quite satisfied with stopping all the trade of London by their mere presence off the Thames, and they had the chance too of picking up homecoming ships that had not been duly warned. So, favoured by fine summer weather, the Dutch admirals cruised backwards and forwards in leisurely fashion between the North Foreland and the outer end of the Gunfleet Sand. They watched with their light craft all the channels that traverse the tangle of sandbanks and shallows in the estuary of the river; but their main fleet was generally somewhere off the Essex coast, for on that side of the estuary lay the channels then best known and most used, the Swin and the Black Deep.
The fleet which thus for some three weeks held possession of the very gateway to the Thames numbered seventy-three line-of-battle ships, twenty-six frigates, and some twenty light craft fitted to be used as fireships. By great exertions Monk and Rupert had got together in the lower Thames eighty-seven fighting-ships and a squadron of fireships. Some fifteen more frigates might have been added to the fleet, but it was thought better to leave them unmanned, and use their crews for strengthening those of the larger ships. The fleet assembled at the Nore had full complements this time. The men were eager to meet the enemy, and numbers of young gallants from the Court had volunteered for service as supernumeraries. The "Loyal London," fresh from the builders' hands at Chatham yard, with her crew of eight hundred men, was said to be "the best ship in the world, large or small." Pepys noted that it was the talk of competent men that this was "much the best fleet, for force of guns, greatness and number of ships, that ever England did see." England had certainly need of a good fleet, for she never met on the sea a more capable and determined enemy than the Dutch. In fact, the republic of the United Provinces was perhaps the only state that ever contended on anything like equal terms against England for the command of the sea.
When at last Monk and Rupert were ready to sail they had to wait for a favourable wind and tide, and, with the help of their pilots, solve a somewhat delicate problem. This problem was something like that which a general on land has to solve when it is a question of moving a large force through defiles of which the other end is watched by the enemy's main army. But it had special complications that the soldier would not have to take into account.