Siege of Breda (1637) when word came that the Dutch had suddenly invested the city of Breda with a besieging army of 18,000. Breda was the capital city of the baronial fief that had once been the crown jewel in the Dutch estates of the Nassau family in the Habsburg Netherlands before the war started. Frederick Henry had therefore a personal interest in recapturing the city and its surroundings. The siege was preceded by an attempt to surprise the garrison on 21 July 1637 by Dutch cavalry under Henry Casimir I of Nassau-Dietz. However, the gates were closed in time and the Dutch skirmishers
Siege of Breda (1624) with modern defences. Thus, in 1531 he inspired the construction of the late medieval style walls of Breda. These were later replaced by modern fortifications. In 1587 and 1622, the defences were further expanded and updated. The Breda fortress consisted of a very high earthen thoroughfare with 15 bastions and a moat. The 55 to 117 meter wide canal was five feet deep and was provided with water from Mark. Access to the city was made possible by four brick gates. Crescent ravelins were applied in the ditches. Hornwork was placed on the gates and at the . Stakewall were