of ventilation and installation of gas-tight rooms. The forts also served as warehouses. Furthermore, the defence was strengthened by the anti-tank ditch, which ran from Berendrecht (at the former redoubt Berendrecht) to the Albert canal at Massenhoven. The anti-tank ditch runs in a circle around Antwerp at a distance of 15 km from Antwerp centre. The length is 33 km. The anti-tank ditch has 15 locks to regulate the water level. These locks were defended by bunkers. Of these thirteen were built, two of which have since been scrapped. The two remaining locks were defended by nearby forts or redoubts. The lock bunkers were armed with three 13.2 mm machine guns. 1940 In the Second World War, the forts played a limited role. After the attack on Belgium, the Belgian army retreated on May 14 behind the Albert Canal to the defense line Koningshooikt-Wavre. Because the Germans on May 13 broke the Maginot Line at Sedan, the army decided to withdraw further and abandon Antwerp and the Koningshooikt-Wavre line. On May 16 and 17 several forts came into action primarily to cover the retreat of the army to the Westhoek. The Germans maintained the fortifications well during World War II. Some were used as storage. Fort Breendonk was used as a transit camp for deportation to Germany. In Fort Breendonk (ca. 300) executions were carried out. Currently, Fort Breendonk is a national memorial. Present The small forts 1–7 were demolished during the construction of the Brialmont wall, except fort 2, of which the reduit is part of the current sports arena. The Brialmont forts 2–8 still exist. Fort 1 (Wijnegem) has been demolished in 1959 (when it was 100 years old) during the construction of the shopping centre Wijnegem and the extension of the roads N12 and R11. Of the forts of the Act of 1870 the forts Merksem, Kruibeke, St. Philip and Zwijndrecht still exist. Fort De Perel was blown up in the Second World War by the Germans. The last remains were demolished in 1958. All forts from the period 1877–1883 (Walem, Lier, Steendorp (formerly also called Rupelmonde), Schoten) are extant. Of the period 1883–1893 the redoubts in Duffel and Kapellen remain. The redoubts Oordenen and Berendrecht were demolished in connection with expansion of the port of Antwerp. All forts built between 1906 and 1914 still exist. Redoubt Massenhoven was demolished for the construction of a reservoir along