Andoy was upgraded in the 1930s to become part of the fortified position of Namur in an attempt to forestall or slow an attack from Germany.

The principal armament was concentrated in the central massif, closely grouped in a solid mass of concrete.

The service areas were placed directly opposite the barracks, which opened into the ditch in the rear of the fort (i.e., in the face towards Namur), with lesser protection than the front and "salient" sides.

[6][7] The fort's heavy guns were German, typically Krupp, while the turret mechanisms were from a variety of sources.

Heavy damage caused panic in the garrison, but the fort continued to hold out with help from supporting infantry.

The utility plant was knocked out entirely, leaving the fort with no electricity or ventilation, and the air quickly became unbreathable.

Artillery fire stopped in the afternoon of the 23rd, and the interval troops and three functioning 57mm turrets repelled a German infantry assault.

Commandant Nollet assembled his 215 remaining men, sabotaged his last functioning armament and surrendered at 1115 hours to the 11th Battalion of the German 32nd Infantry.

[8] By 1916 the fort's latrines and bakery had been moved for better protection, the postern and main entry were reinforced, and ventilation had been substantially improved.

[9] Andoy's armament was upgraded in the 1930s to become part of the Fortified Position of Namur, which was planned to deter a German incursion over the nearby border.

Some of the observation positions were destroyed by German fire, but enough remained in operation to allow coordination with the neighboring forts.

The garrison noted that the fort's eclipsing turrets could not rise fast enough to avoid being hit by 37mm anti-tank guns before they could fire.

Saint-Héribert, Maizeret and Malonne surrendered, and Andoy's armament was reduced to one 75mm gun and a grenade launcher turret.

The Germans delivered an ultimatum under a flag of truce, demanding the surrender of the fort and threatening aerial bombardment.

Andoy's remaining weapons were sabotaged and the fort was surrendered by Commandant Degehet at 1730, receiving military honors from the Germans.