Designed by the British as a means of attacking German patrols in the north-west German coast, the encounter at Heligoland Bight on 28 August 1914 comprised the first naval battle of the war.
The Harwich Force of two light cruisers, HMS Fearless and HMS Arethusa, accompanied by 31 destroyers, made a raid upon German shipping located close to the German naval base at Heligoland.
Acting as cover for the Harwich Force was the First Battle Cruiser Squadron, recently arrived from Scapa Flow and under the command of Vice Admiral Beatty. His squadron consisted of the battlecruisers HMS New Zealand and HMS Invincible, plus three cruisers.
The Harwich Force began the action by sinking two German torpedo boats at around 7am on 28 August. Not entirely surprised by the British attack, the Germans hastily deployed the SMS Frauenlob and the SMS Stettin, joined shortly afterwards by four other light cruisers, including Rear Admiral Mass's flagship, SMS Köln.
Finding his force outgunned by the German defence and under increasing fire, with the Arethusa heavily damaged, Commander Tyrwhitt called Beatty for urgent assistance at 11.25am. Beatty, some 25 miles to the north, hurried to Tyrwhitt's assistance, arriving at 12.40pm. In time to save Tyrwhitt, Beatty's squadron sunk SMS Mainz, SMS Köln, and SMS Ariadne and damaged a further three other cruisers.
Retreating hurriedly under the cover of mist, the Germans had lost 1,200 men, as opposed to just 35 British fatalities.
N.B. Note that the Battle of Heligoland was a naval engagement between the Austrian and Danish navies fought during the first Schleswig War, on 9 May 1864, which was the last naval battle fought by lines of wooden ships - the Danes forced the Austrians to withdraw to neutral waters around the then-British island of Heligoland.