When Germany Turned Warships Into Floating Anti-Aircraft Fortresses

After the scuttling of the High Seas Fleet at Scapa Flow and the harsh limitations imposed by the Treaty of Versailles, Germany’s post–World War I navy—the Reichsmarine—was left with a pitiful force of aging warships. Among them were six obsolete light cruisers, including Arcona and Medusa. As the Kriegsmarine rebuilt during the interwar years, these outdated vessels were pushed into unconventional roles—most notably as floating anti-aircraft platforms during World War II.

In today’s video, we explore one of the most unusual adaptations in naval history: the transformation of obsolete cruisers and captured foreign ships into stationary AA batteries. From the Norwegian coastal defense ships Tordenskjold and Harald Haarfagre to the Dutch cruiser Gelderland and coastal defense ship Hertog Hendrik, the Germans repurposed these ships with varying degrees of success. However, we focus particularly on Arcona and Medusa, two surviving light cruisers from the Imperial era that were extensively rebuilt to serve as mobile AA forts guarding major German naval bases.

You'll learn how Arcona was refitted at Deutsche Werke in Kiel in mid-1940, stripped of her propulsion system, and anchored at Wilhemshaven and later Brunsbüttel to provide anti-aircraft protection using six 10.5cm guns, 2cm flak cannons, and radar systems. Medusa, meanwhile, underwent a similar conversion by Rickmers in Wesermünde and saw action as part of the Marine-Flak-Abteilung defending Wilhemshaven, although her career was plagued by tugboat collisions and mechanical woes.

We also touch on the confusing renaming conventions the Kriegsmarine applied to the captured ships, reusing the names of old cruisers to create a baffling naval paper trail. Ultimately, these ships were deemed Category C “wrecks” by Allied commissions after the war and slated for destruction, although the Soviets delayed some of their fates.

This episode dives deep into the practical ingenuity—and occasional desperation—of German wartime ship conversion strategy. By reusing aged and captured hulls to boost anti-air capabilities, the Kriegsmarine attempted to protect its shrinking naval infrastructure from constant Allied air raids.

Join us as we explore how these forgotten ships fought their final battles not at sea, but anchored in place, guns turned skyward. Like and subscribe if you enjoy hidden naval history, captured warships, and the fascinating afterlives of obsolete vessels!

Sources/Other Reading:

https://www.amazon.com/Warship-2023-J...

https://www.amazon.com/Northern-Theat...

https://hmsjervisbay.com/Story.HX84.php

https://www.amazon.com/German-Light-C...

https://www.amazon.com/Heavy-Cruisers...

https://www.amazon.com/Spoils-War-Ene...

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