 In particular, a lack of nighttime illumination required that construction be stopped at the end of each day, and a poor understanding of the bonding properties of concrete caused weak points between daily pours of concrete, causing layers of concrete to separate under stress of bombardment or explosion.These faults were cured with the reconstruction of other forts, the use of reinforced concrete, and with the construction of four new forts facing the German frontier to the east of Liége.The largest of these was Fort Eben-Emael, which would play a significant role at the beginning of the Second World War.