To defend the nation against foreign attacks, a series of forts were built around Antwerp, Liège and Namur from the end of the nineteenth century. For example, the Defense Line of Antwerp consisted of sixteen larger strongholds in a wide circle around the city, including Fort Breendonk.

In the 1950s, anyone who wanted to cross the Upper Merwede had to rely on a ferry service. This was not very convenient in emergencies.