On 2 May 1915 Lohs was promoted to Oberleutnant zur See. For one month Lohs was second radio officer on the battlecruiser , then he moved to U-Bootschule for two months. Afterwards he became a monitoring officer at the torpedo boat division. On 6 December he became commander of , on which he did 9 patrols along the British coast. On 2 January 1918 he became Commanding officer of , taking over the command of this boat from another legendary U-boat commander, Otto Steinbrinck. "Lohs" had also some very good ideas on U-boat warfare and new tactics and on 24 April 1918 he received postum the Pour le Mérite.