At the outbreak of the First World War in 1914, Antwerp stood as the national stronghold. From here, the Belgian king and the army were to lead the defense of the country, and the city was so well fortified that it was deemed impregnable.

However, things would take a completely different turn, and a crucial role in this reversal was played by an unexpected superweapon: the world-famous Big Bertha, officially known as the "Kurze Marine Kanone" or KMK.

The cannon was developed in utmost secrecy, and at the start of the war, both Belgian and foreign defense experts were convinced that such heavy artillery simply could not exist. However, it did exist, and its deployment was a complex operation. The cannon was dismantled into five parts, transported separately, and the entire assembly had to be anchored to a concrete base to absorb the recoil, or the entire cannon would be driven meters deep into the ground.

Big Bertha fired projectiles of a whopping 420 mm, weighing 800 kg or more, with an impressive range of 10 km. This allowed them to be positioned beyond the reach of Belgian artillery, which was limited to 8.4 km. The forts of Pontisse and Loncin around Liège had already fallen victim to Big Bertha, and from September 28, this colossal cannon turned its attention to Antwerp.

Four Big Berthas were deployed against Antwerp, and it quickly became evident that the Belgian forts were no match for the overwhelming power. The concrete structures simply were not strong enough to withstand the 42 cm shells.

Ultimately, the KMKs were directed towards the forts of Sint-Katelijne-Waver, Lier, Kessel, and Koningshooikt (the fort of Walem fell without the use of Big Bertha), causing the once-considered impregnable fortress to withstand only five days against the German artillery onslaught. On October 3, the Belgian army decided to withdraw. Through the intervention of the English, the departure would be delayed for a while, but on October 7, the king and the army definitively left Antwerp.

On October 8, the bombardment of the city itself began, but that is a story for another time...