She saw limited active duty during her service career with the German fleet due to the relatively peaceful nature of the late 19th and early 20th centuries.

These training maneuvers were nevertheless very important to developing German naval tactical doctrine in the two decades before World War I, especially under the direction of Alfred von Tirpitz.

In a state of severe disrepair, the old battleship was partially disarmed after the Ottoman Empire joined the Central Powers early in World War I.

Though they were the first modern battleships built in Germany, presaging the Tirpitz-era High Seas Fleet, the authorization for the ships came as part of a construction program that reflected the strategic and tactical confusion of the 1880s caused by the Jeune École (Young School).

This operation had political motives; Germany had only been able to send a small contingent of vessels—the protected cruiser Kaiserin Augusta, the coastal defense ship Hagen, and the screw frigate Stosch—to an international naval demonstration off the Moroccan coast at the same time.

The fleet then steamed through the Skagerrak to the Baltic; heavy storms caused significant damage to many of the ships and the torpedo boat S41 capsized and sank in the storms—only three men were saved.

Following the conclusion of the maneuvers, Kurfürst Friedrich Wilhelm again went into dock for maintenance, and while she was out of service, Koester transferred his flag to Sachsen from 16 September to 3 October.

The typical routine was interrupted in early August when Wilhelm II and Augusta went to visit the Russian imperial court at Kronstadt; both divisions of I Squadron were sent to accompany the Kaiser.

While steaming back to Kiel, a severe storm hit the fleet, causing significant damage to many ships and sinking the torpedo boat S58.

The exercises started in the Baltic and on 30 August the fleet passed through the Kattegat and Skagerrak and steamed into the North Sea for further maneuvers in the German Bight, which lasted until 7 September.

The expeditionary force consisted of Kurfürst Friedrich Wilhelm and her three sisters, six cruisers, 10 freighters, three torpedo boats, and six regiments of marines, under the command of Generalfeldmarschall (Field Marshal) Alfred von Waldersee.

From there, Wörth was detached to cover the disembarkation of the German expeditionary corps outside the Taku Forts, while Kurfürst Friedrich Wilhelm and her other two sister ships joined the blockade of the Yangtze River, which also included a British contingent of two battleships, three cruisers, four gunboats, and one destroyer.

[25] By the time the German fleet had arrived, the siege of Beijing had already been lifted by forces from other members of the Eight-Nation Alliance that had formed to deal with the Boxers.

[26] In early September, Kurfürst Friedrich Wilhelm and the rest of the German fleet was moved to the Yellow Sea, where Waldersee, who had been given command of all ground forces of the Eight-Nation Alliance, planned stronger actions against the harbors of northern China.

[29] Kurfürst Friedrich Wilhelm went to Kiel after returning from the expedition to China, where on 14 August KAdm Fischel raised his flag aboard the ship.

Kurfürst Friedrich Wilhelm then participated in the annual autumn maneuvers, after which she was decommissioned, with the new battleship Wittelsbach taking her place as second command flagship.

The plans had initially called for the center 28 cm turret to be replaced with an armored battery of medium-caliber guns, but this proved to be prohibitively expensive.

Kurfürst Friedrich Wilhelm served as the second command flagship in I Squadron of the newly created High Seas Fleet, but at the end of the 1906 training year, she was removed from active duty and her place was taken by the new battleship Pommern.

[35] Beginning on 1 October 1907, Kurfürst Friedrich Wilhelm was assigned to the Reserve Squadron in the North Sea, which had been created in early 1907 to train new crews.

The battleship was scheduled to take part in the autumn maneuvers, but shortly before the fleet assembled for the exercises, both she and Weissenburg were sold to the Ottoman Empire.

After lengthy negotiations, including Ottoman attempts to buy one or more of the new battlecruisers Von der Tann, Moltke, and Goeben, the Germans offered to sell the four ships of the Brandenburg class at a cost of 10 million marks.

During the war, Barbaros Hayreddin conducted gunnery training along with the other capital ships of the Ottoman navy, escorted troop convoys, and bombarded coastal installations.

[50] The Ottoman fleet sortied from the Dardanelles at 9:30; the smaller craft remained at the mouth of the straits while the battleships sailed north, hugging the coast.

The Greek flotilla, which included the armored cruiser Georgios Averof and three Hydra-class ironclads, sailing from the island of Lemnos, altered course to the northeast to block the advance of the Ottoman battleships.

[52] Barbaros Hayreddin, Turgut Reis, and other units of the Ottoman fleet departed the Dardanelles at 8:20 on the morning of 18 January, and sailed toward the island of Lemnos at a speed of 11 knots (20 km/h; 13 mph).

[52] Georgios Averof, with the three Hydra-class ironclads and five destroyers trailing behind, intercepted the Ottoman fleet approximately 12 nautical miles (22 km; 14 mi) from Lemnos.

On 3 August 1914, Barbaros Hayreddin began a refit at Constantinople—German engineers inspected her and other Ottoman warships in the dockyard and found them to be in a state of severe disrepair.

[60] By early November, the actions of the German battlecruiser Goeben, which had been transferred to the Ottoman Navy, resulted in declarations of war by Russia, France, and Great Britain.

On 7 August, the British landed more troops at Suvla Bay, prompting the high command to send Barbaros Hayreddin to support the Ottoman defenses there.

[63] The next day, while she was en route to the area with only a single torpedo boat as escort, she was intercepted by the British submarine HMS E11[64] off Bolayır in the Sea of Marmara.