By the end of the year 1666, however, both nations had become weary of the war, and the King of Sweden having offered his mediation, it was readily accepted by both sides. Negotiations were immediately set on foot which ultimately resulted in the treaty of Breda; but in the meantime the Dutch rather increased than relaxed their efforts to strengthen their navy, hoping thereby to influence the terms of the treaty in process of negotiation. Having previously sounded the mouth of the Thames to ascertain how far it might be practicable to attempt to enter it with large ships, and having thereby discovered the facility with which such a project could be carried out, De Witte determined to make the attempt without delay. The Dutch fleet being ready, sailed over to the English coast, where it was joined by Van Ghent, and formed a fleet of seventy men-of-war, besides fire-ships. On June 7th they attacked Sheerness, which was at that time unfinished and in no state of defence, and captured fifteen iron guns and a considerable quantity of naval stores. The Duke of Albemarle, Sir Edward Spragge, and other officers had made all imaginable provision for the defence of the River Medway, by sinking ships in the passage, throwing a chain across it, and placing three large vessels, which had been taken from the Dutch, behind the chain. The Dutch, however, had the advantage of a strong easterly wind, which encouraged them to make an attempt upon our ships at Chatham, in spite of the precautions taken to preserve them. It was on June the 12th that they executed this design; which, however, would have miscarried at last, if one Captain Brakell, who was a prisoner on board their fleet for some misdemeanour, had not offered to wipe out the memory of his former mistake by breaking the chain, a service which he gallantly performed. Captain Brakell also with great bravery boarded and took one of the English frigates which guarded the passage; and soon after, the _Matthias_, the _Unity_, and the _Charles the Fifth_, the ships which had been taken from the Dutch, were set on fire. The next day, the advantage of wind and tide continuing, the Dutch advanced with six men-of-war and five fire-ships as high as Upnore Castle; but were so warmly received that they were obliged to return. However, as they came back, they burnt the _Royal Oak_, a very fine ship, and in her Captain Douglas, who chose to be burnt with her rather than live to be reproached with having deserted his command. On the 14th they carried off the hull of the _Royal Charles_, notwithstanding all the English could do to prevent it; a project which they had dearly at heart. On their return, two Dutch men-of-war ran ashore in the Medway and were burnt, which, with eight fire-ships consumed in the action and one hundred and fifty men killed, is all the loss acknowledged by the Dutch writers; though it is not improbable that they really suffered much more.