 The 1648 Peace of Münster permanently closed the Scheldt estuary, benefiting De Witt's power base of Amsterdam by eliminating their closest rival, Antwerp; ensuring it remained shut was a vital objective.Changes in this region also concerned England, since control of ports on the North Flemish coast allowed a hostile power to blockade the Channel.In 1665, an attack by the Duke of York on the West-Indische Compagnie led to the Second Anglo-Dutch War; in the first 18 months, the Dutch suffered a serious naval defeat at Lowestoft, an invasion by Münster and an attempted Orangist coup, both financed by England.