The English Parliament had passed the first of the Navigation Acts in October 1651, aimed at hampering the shipping of the highly trade-dependent Dutch. Agitation among the Dutch merchants had been further increased by George Ayscue's capture in early Barbados in contravention of an embargo. Both sides had begun to prepare for war, but conflict might have been delayed if not for an unfortunate encounter on 29 May1652 (19 May in the Julian calendar then in use in England) near the Straits of Dover between a Dutch convoy escorted by 40 ships under Admiral Maarten Tromp and an English fleet of 25 ships under General-at-Sea Robert Blake.
An ordinance of Cromwell required all foreign fleets in the North Sea or the Channel to dip their flag in salute, but when Tromp refused, Blake opened fire. Tromp replied with a broadside from his flagship Brederode, and a five hour battle ensued. The English sank two Dutch ships, but as darkness fell the Dutch fleet withdrew and Tromp escorted the convoy to safety.