Admiral Alfred von Tirpitz reacted to this development with the request for newer and stronger capital ships.

In May 1906, the Reichsmarineamt (RMA, Imperial Navy Office) received word that the British were building battleships equipped with 13.5-inch (34 cm) guns.

[4] Tirpitz's hesitation at increasing the armament of the new ships was lost when it became known in early 1907 that the United States Navy was building battleships with 30.5 cm guns.

In March 1907, Tirpitz ordered the Construction Department to prepare a design with 30.5 cm guns and 320 mm (13 in) thick belt armor.

Tirpitz favored adopting this arrangement for the Helgoland class, but the Construction Department felt two superfiring turrets could be easily disabled by a single hit.

The reduction necessitated the replacement of the coastal defense ships of the Siegfried and Oldenburg classes as well as the Brandenburg-class battleships.

[c] At full fuel capacity, the ships could steam for 5,500 nautical miles (10,200 km; 6,300 mi) at a speed of 10 knots (19 km/h; 12 mph).

[6] Like the Nassau class which preceded it, the Helgoland-class ships carried their main armament in an unusual hexagonal configuration.

The only major differences were slight increases in the armor protection for the main and secondary batteries, and a much thicker roof for the forward conning tower.

SMS Oldenburg, the final vessel, was built by Schichau in Danzig; she was laid down 1 March 1909, launched 30 June 1910, and commissioned on 1 May 1912.

[13][15] The Helgoland-class ships operated as a unit in the High Seas Fleet; they served as I Division of I Battle Squadron.

The ships of the class participated in several fleet operations in the North Sea, including the sortie on 31 May 1916 that resulted in the Battle of Jutland.

The ships also saw limited service in the Baltic Sea, primarily during the abortive Battle of the Gulf of Riga in August 1915.

The first major operation of the war in which the Helgoland-class ships participated was the raid on Scarborough, Hartlepool and Whitby on 15–16 December 1914.

The Helgoland-class ships, along with the Nassau, Kaiser, and König classes steamed in distant support of Franz von Hipper's battlecruisers.

"[20] The captain of the battlecruiser Moltke was even more scathing; he stated that Ingenohl had turned away "because he was afraid of eleven British destroyers which could have been easily eliminated ...

"[20] The Helgoland-class ships also sortied from port to support the German battlecruisers during the Battle of Dogger Bank, but did not actively engage British forces.

[21] On 3 August 1915, several heavy units of the High Seas Fleet were transferred to the Baltic to participate in a planned foray into the Riga Gulf.

The German forces, under the command of Vice Admiral Hipper, included the four Nassau and four Helgoland-class battleships, the battlecruisers Seydlitz, Moltke, and Von der Tann, and a number of smaller craft.

For the duration of the operation, the ships were stationed outside the gulf in order to prevent Russian reinforcements from disrupting the laying of minefields.

This delay was compounded by stiff resistance from the Russian navy; Deutschland was ultimately unable to lay her mines.

Reports of Allied submarine activity in the area prompted the withdrawal of the German naval force on the morning of 20 August.

Ostfriesland, Helgoland, and Thüringen began firing on HMS Warspite, which, along with the other Queen Elizabeth-class battleships of the 5th Battle squadron, had been pursuing the German battlecruiser force.

[27] With the exception of Ostfriesland, the firing only lasted for four minutes, because the German line had been in the process of turning to the east-northeast, and the ships quickly lost sight of the British battleships.

The shell tore a 20-foot (6.1 m) hole in the hull and rained splinters on the foremost port side 5.9 in gun; approximately 80 tons of water entered the ship.

[31] At around midnight on 1 June, the Helgoland- and Nassau-class ships in the center of the German line came into contact with the British 4th Destroyer Flotilla.

Thüringen opened fire first and pummeled Black Prince with a total of 27 heavy-caliber shells and 24 rounds from her secondary battery.

[34] [Black Prince] presented a terrible and awe-inspiring spectacle as she drifted down the line blazing furiously until, after several minor detonations, she disappeared below the surface with the whole of her crew in one tremendous explosion.

[35] Following the return to German waters, Helgoland and Thüringen, along with the Nassau-class battleships Nassau, Posen, and Westfalen, took up defensive positions in the Jade roadstead for the night.

[21] Ostfriesland was ceded to the US Navy, and was later used as a stationary target during a demonstration of air power, conducted by General Billy Mitchell on 21 July 1921 off Cape Henry in Virginia.