Oldenburg

The battleships of the Helgoland class were the last German battleships with steam expansion engines and build as replacements for old armored ships and coast defense ships. Although it was considered to use steam turbines for the next battleships after the Nassau class, the development of turbines did not reach the state to produce powerful and reliable turbines for such ships.

As a result of this, those ships were basically enlarged ships of the Nassau class, with the same hexagonal positions of the main artillery turrets. This was not without contradiction in the German navy since only 2/3rd of the 30,5 cm guns could be used for broadside fire. In addition to the enhanced gun size - it grew from 28 cm to 30,5 cm -, the internal subdivision and armor protection were also improved.

All four ships served in the 1st Battleship Squadron of the Imperial Navy and took part in all major fleet operations. They were only lightly damaged during the Battle of Jutland and were not interned at Scapa Flow unlike most other Imperial Navy ships. All expect the Ostfriesland were scrapped after the war, while the Ostfriesland had an unique fate: It was the first battleship that was sunk by aircraft during weapons tests in the USA in 1921.