 The aim of the campaign was an ambitious one - the capture of the strong fortress of Maastricht, which was deep in Spanish-held territory.As Prince Henry marched south, the fortified places of Venlo and Roermond capitulated with very little resistance thanks to the efforts of the Stadtholder of Upper Gelderland, Van der Bergh, who was sympathetic to the Dutch cause.In 1632 Maastricht was ringed by tall medieval walls with a large number of towers.