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.

The garrison, commanded by Guillaume de Bette, baron of Lede, was strong, loyal to Spain and determined to resist the Dutch army.

In response to the investment of Maastricht, Isabella (the Governess of the Spanish Netherlands) recalled her troops from the Palatinate and sent Don Gonzalo Fernández and the Marquis of Santa Cruz to relieve the town.

The Spanish arrived near Maastricht on 2 July with 18,000 infantry and 6,000 cavalry, but though they outnumbered Frederick Henry's army, they were unwilling to attack the Dutch lines on account of their strength.

This plan was well-conceived but in the end the strength of Frederick Henry's lines of contravallation and the superior morale of his troops (who were encouraged by his presence during the fighting) decided the day.

Having failed to raise the siege by force of arms, Don Gonzalez and Pappenheim decided to cut the Dutch supply lines and so starve them out of their strong position.

Frederick Henry's feat in capturing Maastricht dismayed the Spanish, who made negotiations for peace, but their resolve was stiffened a few months later by the death of the Swedish Protestant hero Gustavus Adolphus at the Battle of Lützen on 16 November.