The 1697 Treaty of Ryswick permitted the Dutch to garrison a number of cities, including Namur and Ypres, but in February 1701, the French quickly occupied them. Re-establishing the Barrier was the primary Dutch objective during the War of the Spanish Succession and was specified in Article 5 of the Treaty of The Hague (1701), which reformed the Grand Alliance. The Barrier also had an economic element, since the 1648 Peace of Münster gave the Dutch a monopoly over the Scheldt and made its extent a matter of debate, particularly with Britain. The Scheldt estuary was a key transportation point for European import and export. Its control was a valuable commercial asset and allowed the merchants of Amsterdam to undermine the trade of the commercial rival, Antwerp, severely.