Kelly served in the First World War: on 4 August 1914 he was assigned, as commanding officer of HMS "Dublin", by Sir Berkeley Milne to shadow the German squadron under Rear-Admiral Wilhelm Souchon, consisting of the cruiser SMS "Breslau" and the battlecruiser SMS "Goeben". Kelly did so, but eventually lost sight of the German ships. Kelly's younger brother Howard, commanding the cruiser HMS "Gloucester", also became involved in the subsequent chase. HMS "Dublin" re-encountered the Germans at 1.30 a.m. on 6 August 1914 while sailing to join Rear-Admiral Ernest Troubridge's squadron, and passed news of the sighting to his brother and to Troubridge, before losing them again. Howard Kelly continued to shadow the Germans, and at 8.30 p.m. Milne ordered HMS "Dublin", sailing in company with two destroyers, to launch a torpedo attack that night. Using the reports from HMS "Gloucester" of the Germans' speed and course, HMS "Dublin" and the destroyers took up position on the Germans' bow, and waited to intercept them. They hoped to make contact at 3.30 a.m. on the morning of 7 August 1914, but the British had been spotted by SMS "Breslau", which warned SMS "Goeben". The Germans passed unseen to starboard.