On 10 May 1940, German forces attacked the new Belgian forts, quickly neutralising Eben-Emael by airborne assault. The three other forts were bombarded by 305 mm howitzers and dive-bombers and each repulsed several infantry assaults. Two of the forts surrendered on 21 May and the last, Fort de Battice, on the following day, having been by-passed by the main German thrust. Modernised French polygonal forts at Maubeuge were attacked on 19 May and were surrendered after their gun turrets and observation domes had been knocked out with anti-tank guns and demolition charges. Late in the war, the ring fortifications of Metz were hastily prepared for defence by German forces and was attacked by the Third Army in mid-September 1944 in the Battle of Metz; the last fort surrendered nearly three months later.