In December 1664, the English fleet attacked the Dutch Smyrna fleet. Though the attack failed, the Dutch in January 1665 allowed their ships to open fire on English warships when threatened. War was declared by the Dutch on 4 March 1665, following two further English attacks on Dutch convoys, one off Cadiz and another in the English Channel. The Dutch fleet was confident of victory, but it contained a significant proportion of older or weak ships. In the first year of the Second Anglo-Dutch War, at the Battle of Lowestoft on 13 June 1665, the Dutch suffered the worst defeat in the history the Dutch Republic's navy. At least sixteen ships lost, and one-third of its personnel captured or killed; Van Wassenaer was among the dead.