SMS Hagen was the final vessel of the six-member Siegfried class of coastal defense ships (Küstenpanzerschiffe) built for the German Imperial Navy.

Hagen was built by the Kaiserliche Werft (Imperial Shipyard) in Kiel between 1891 and 1893, and was armed with a main battery of three 24-centimeter (9.4 in) guns.

General Leo von Caprivi, the new Chef der Admiralität (Chief of the Admiralty), requested a series of design proposals, which ranged in size from small 2,500 t (2,461-long-ton) coastal defense ships to heavily armed 10,000 t (9,800-long-ton) ocean-going battleships.

Caprivi ordered ten coastal defense ships to guard the entrances to the canal, since even opponents of the navy in the Reichstag (Imperial Diet) agreed that such vessels were necessary.

For defense against torpedo boats, the ship was also equipped with a secondary battery of eight 8.8 cm (3.5 in) SK L/30 guns in single mounts.

[5][6] Hagen was immediately ordered to sail for Morocco in response to an international incident that followed the murder of two German merchants in the country.

There, she joined the protected cruiser Kaiserin Augusta, and the old corvettes Marie and Stosch; the German government had demanded 250,000 marks as an indemnity, and the naval squadron was sent to secure it.

She returned to the Reserve Division in 1897, and from 3 August to 25 September, operated with the newly formed II Battle Squadron during the fleet maneuvers, along with her five sister ships.

During this period, Hagen served as the flagship of Konteradmiral (KAdm—Rear Admiral) Volkmar von Arnim, one of the squadron's two divisional commanders.

She continued to operate with the squadron in 1898; during training exercises in May, Hagen suffered a boiler explosion on the 31st, forcing her to withdraw from the maneuvers.

Work was completed in late 1900, and she began sea trials on 2 October under the command of KK Carl Paschen.

Hagen was reactivated only once in the next ten years, to take part in fleet maneuvers in 1909, which began on 22 July and concluded on 15 September; she thereafter returned to the reserve.

[10] Following the start of World War I in July 1914, Hagen was mobilized for wartime service, being recommissioned on 12 August under the command of FK Lebrecht von Klitzing.

Hagen took part in coastal patrol duty from 29 September to 13 December, alternating between the Jade Bight and the mouth of the Weser.

When the battlecruisers of I Scouting Group conducted the Raid on Yarmouth on 2–3 November, Hagen and the other ships were sent to the outer Jade roadstead to cover their return.

In the early hours of 4 November, as I Scouting Group returned to the Jade, Hagen came to the aid of the sinking armored cruiser Yorck, helping to evacuate more than half of her crew.

[11][13] Beginning in June 1916, she was employed as a barracks ship initially in Libau, to support U-boat crews stationed in the Baltic.

She was towed to Danzig on 19 August to serve as a barracks for the crew of the old pre-dreadnought battleship Lothringen, which was at that time on patrol duty in the Danish straits.