shellfire equaling their heaviest guns: 21 cm. The top of the central massif used of unreinforced concrete, while the caserne walls, judged to be less exposed, used . Under fire, the forts were damaged by 21 cm fire and could not withstand heavier artillery. Armament Embourg's armament included a Grüsonwerke turret with a single 21 cm Krupp gun, a 15 cm Creusot turret with twin guns and a 12 cm Châtillon-Commentry turret with two Krupp guns, all for distant targets. Four Grüsonwerke 57 mm gun turrets were provided for local defense. The fort also mounted an observation turret with a searchlight. Nine rapid-fire 57 mm guns were provided in casemates for the defense of the ditches and the postern. The fort's heavy guns were German, typically Krupp, while the turret mechanisms were from a variety of sources. The fort was provided with signal lights to permit communication with the neighboring Fort de Loncin and Fort de Liers. The guns were fired using black powder rather than smokeless powder, producing choking gas in the confined firing spaces that spread throughout the fort. First World War Liège first came under attack on 6 August 1914. When the Liège's fortifications proved unexpectedly stubborn, the Germans brought heavy siege artillery to bombard the forts with shells far larger than they were designed to resist. Embourg was heavily bombarded starting 12 August. The fort surrendered the next day after 48 hours of bombardment. Occupying the fort during the remainder of the war, Germans made a number of improvements to the fort in 1914 and 1915. Fortified Position of Liège Embourg's armament was upgraded in the 1930s to become part of the Fortified Position of Liège II, which was planned to deter a German incursion over the nearby border. The armament was upgraded with new guns in the turrets and an anti-aircraft battery. This was accompanied by improvements to ventilation, protection, sanitary facilities, communications and electrical power. An infantry shelter with an automatic rifle cloche was built at this time, as well as a remote air intake tower some distance to the west of the fort, linked to the fort by a tunnel. In 1940 the fort's garrison comprised 323 men, mostly reservists, with four officers. Second World War Embourg first came into contact with German forces during the Battle of Belgium on 12 May 1940. The fort was surrounded on the 13th, occupying areas around