In the first decade of the 20th century, the Imperial German Navy had generally ordered twelve large torpedo boats (Große Torpedoboote) as part of each year's construction programme, with a gradual evolution of design in each year's orders, with speed, range and seaworthiness improving year-on-year.

For the 1911 fiscal year's orders, it was decided to revert to a smaller design, with the numbering system for torpedo boats restarting as a consequence.

[9][10] G12 remained the leader of the 5th Torpedo boat flotilla of the German High Seas Fleet on the outbreak of war.

[11] On 28 August 1914, the British Harwich Force, supported by light cruisers and battlecruisers of the Grand Fleet, carried out a raid towards Heligoland with the intention of destroying patrolling German torpedo boats.

[12] The German defensive patrols around Heligoland consisted of one flotilla (the 1st Torpedo-boat Flotilla) of 12 modern torpedo boats forming an outer patrol line about 25 nautical miles (29 mi; 46 km) North and West of Heligoland, with an inner line of older torpedo boats of the 3rd Minesweeping Division at about 12 nautical miles (14 mi; 22 km).

The British light cruiser Arethusa and destroyers Laurel, Laertes and Liberty were badly damaged but safely returned to base.

[22] On 8 September 1915, the 5th and 9th Torpedo Boat Flotillas were on patrol north west of the Horns Reef when G12 suffered a steering failure and rammed V1.