With the German declaration of war in August 1914, all further training at the naval academy was terminated and the normal compulsory officer examination was skipped. The entire Crew 1913 was assigned to various units in the Imperial Navy. Lindemann was assigned to , a battleship which belonged to the 2nd Battle Squadron of the High Seas Fleet under the command of "Vizeadmiral" (vice admiral) Reinhard Scheer, taking on the position of 3rd wireless telegraphy officer. "Lothringen" was mostly tasked with patrolling the North Sea, sailing back and forth between Altenbruch (now part of Cuxhaven) and Brunsbüttel without engaging in combat. Lindemann left "Lothringen" on 1 June 1915 to attend the wireless telegraphy school at Mürwik. He successfully completed the course and returned from it in July 1915. He then took over the position of 2nd wireless telegraphy officer, a position that fellow officers joked suited his abnormally large ears. He was promoted to "Leutnant zur See" (Second Lieutenant) on 18 September 1915.