Named for the region of East Frisia, Ostfriesland's keel was laid in October 1908 at the Kaiserliche Werft dockyard in Wilhelmshaven.

Ostfriesland was assigned to the I Battle Squadron of the High Seas Fleet for the majority of her career, including World War I.

[6] The ship's secondary battery consisted of fourteen 15 cm (5.9 in) SK L/45 guns, all of which were mounted in casemates in the side of the upper deck.

Ostfriesland, named for the north-western coastal area of Germany, was commissioned into the High Seas Fleet on 1 August 1911, just under three years from when work commenced.

[14] During the last peacetime cruise of the Imperial Navy, the fleet conducted drills off Skagen before proceeding to the Norwegian fjords on 25 July.

[20] On the afternoon of 7 September, Ostfriesland and the rest of the High Seas Fleet conducted a training cruise to the island of Heligoland.

That evening, the German battle fleet of some twelve dreadnoughts—including Ostfriesland and her three sisters—and eight pre-dreadnoughts came to within 10 nmi (19 km; 12 mi) of an isolated squadron of six British battleships.

As a result, Kaiser Wilhelm II removed Ingenohl from his post and replaced him with Admiral Hugo von Pohl on 2 February.

Ostfriesland and the rest of the fleet remained in port until 4 August, when I Squadron returned to the Baltic for another round of training maneuvers.

[11] The assault force included the eight I Squadron battleships, the battlecruisers Von der Tann, Moltke, and Seydlitz, several light cruisers, 32 destroyers and 13 minesweepers.

[11] On 23–24 October, the High Seas Fleet undertook its last major offensive operation under the command of Admiral Pohl, though it ended without contact with British forces.

[28] Scheer proposed a more aggressive policy designed to force a confrontation with the British Grand Fleet; he received approval from the Kaiser in February.

At this point, Scheer, who had been warned of the sortie of the Grand Fleet from its base in Scapa Flow, also withdrew to safer German waters.

The opposing ships began an artillery duel that saw the destruction of Indefatigable, shortly after 17:00,[34] and Queen Mary, less than half an hour later.

[35] By this time, the German battlecruisers were steaming south to draw the British ships toward the main body of the High Seas Fleet.

[41] An hour later, the leading units of the German line encountered British light forces and a violent firefight at close range ensued.

[42] Despite the ferocity of the night fighting, the High Seas Fleet punched through the British destroyer forces and reached Horns Reef by 4:00 on 1 June.

[53] On the approach to the English coast during the action of 19 August 1916, Scheer turned north after receiving a false report from a zeppelin about a British unit in the area.

[54] As a result, the bombardment was not carried out, and by 14:35, Scheer had been warned of the Grand Fleet's approach and so turned his forces around and retreated to German ports.

[55] On 25–26 September, Ostfriesland and the rest of I Squadron provided support for a sweep out to the Terschelling Bank conducted by the II Führer der Torpedoboote (Leader of Torpedo Boats).

During Operation Albion, the amphibious assault on the Russian-held islands in the Gulf of Riga, Ostfriesland and her three sisters were moved to the Danish straits to block any possible British attempt to intervene.

[57] Following the capitulation of Germany in November 1918, most of the High Seas Fleet, under the command of Rear Admiral Ludwig von Reuter, was interned in the British naval base in Scapa Flow.

[60] On the morning of 21 June, the British fleet left Scapa Flow to conduct training maneuvers, and at 11:20 Reuter transmitted the order to scuttle his ships.

She was ceded to the United States as war reparations, commissioned on 7 April at Rosyth as USS Ostfriesland and commanded by Captain J. F.

[63] In July 1921, the United States Navy and Army Air Service conducted a series of bombing tests off Cape Henry, led by General Billy Mitchell.

The bombs that nearly missed the ship, however, had done significant underwater damage to the hull, which allowed some flooding and created a list of five degrees to port and three additional feet of draft at the stern.

Inspectors again went aboard Ostfriesland following the fifth attack and noted that the hits had not seriously damaged the ship, though one had created a large hole on her starboard side that allowed further flooding.

The joint Army–Navy report on the tests, issued a month later and signed by General John J. Pershing, stated that "the battleship is still the backbone of the fleet.

The sinking of the battleship sparked great controversy in the American public sphere; Mitchell's supporters exaggerated the significance of the tests by falsely claiming Ostfriesland to be an unsinkable "super-battleship" and that "old sea dogs ... wept aloud.

Mitchell was widely supported in the press, though his increasingly combative tactics eventually resulted in a court-martial for insubordination that forced him to retire from the military.