Geertruidenberg was also important as a border town to protect Holland against the Duchy of Brabant.

[1] In 1323, Willem van Duvenvoorde got orders to build what would become Geertruidenberg Castle.

[1] About 5 kilometers to the south, Van Duvenvoorde also had the formidable Strijen Castle, his residence as Lord of Oosterhout.

[3] The first of the Hook and Cod wars was fought between Margaret of Hainaut and her son William V. It started with an attack by the Bishop of Utrecht.

Meanwhile, the Cod party attacked and quickly conquered a lot of the smaller castles of the Hook lords.

One of the reasons why Geertruidenberg Castle was so strong, was that it was probably very difficult to cut its supply routes.

The Hook Strijen Castle was less than 5 km to the south over a good road.

A simple blockade with a few forces would be dangerous, because these could be surprised by a raiding party from Strijen Castle.

This is proven by the delay between Geertruidenberg switching to the Cod side on 15 June 1351, [4] and the start of the blockade or siege.

A second reason for the strength of Geertruidenberg, was that Willem van Duvenvoorde was a very important leader of the Hook party.

A third reason why Geertruidenberg Castle was so strong remained obscure until very recently.

After the July 1351 Battle of Zwartewaal, William's Cod party had little reason for concern in Holland itself.

[11] The besiegers of Geertruidenberg Castle were led by John IV, Lord of Arkel.

Philips van Polanen and 34 defenders kept their possessions, but chose to go into exile in Breda.

John II of Polanen was the official schout of Geertruidenberg and castellan of its castle.