During the First World War, Manstein served on both the German Western and Eastern Fronts. At the beginning of the war, he was promoted to lieutenant and participated in the invasion of Belgium with the 2nd Guard Reserve Infantry Regiment. In August 1914, he took part in the capture of Namur, the site of a massive citadel surrounded by outlying forts. In September, Manstein's unit was one of two transferred to East Prussia and attached to the Eighth Army, commanded by Hindenburg. After seeing action in the First Battle of the Masurian Lakes, his unit was soon reassigned to the Ninth Army, which was in the process of advancing from Upper Silesia to Warsaw. Overstretched, the Ninth Army was forced to withdraw in the face of a Russian counterattack, and on 16 November, Manstein was wounded during the retreat when he was among a detachment that stormed a Russian entrenchment. He was shot in the left shoulder and the left knee; one bullet hit his sciatic nerve, causing the leg to be numb. Recovery took six months in hospital in Beuthen and Wiesbaden.