When the U boats were unleashed on the world's shipping

U-boat - Wikipedia

Red Sea conflict: Dozens of Canadian ships delayed

The WW1 Q-Ships Were Heavily-Armed Decoy Vessels, Designed To Lure Unsuspecting U-Boats Into A Trap

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The Forgotten Surrender: World War I and the German U-boat fleet, by Rebecca Jane Morgan

U-boat, German Submarine Warfare in WWI & WWII

Did the design and propulsion of the German Navy's Type XXI U Boat influence post World War Two submarine design? - Quora

Sea History 184 - Fall 2023 by National Maritime Historical Society & Sea History Magazine - Issuu

German WW1 U-Boat Campaign That Almost Broke UK

Power Unleashed: Epic Warships in the Future Seas Stock Illustration - Illustration of innovation, design: 279796210

Germany brought WWII to the Florida coast in 1942

Red Sea crisis: Can EU warships deter Houthi rebels? – DW – 01/21/2024

Kaiten - Warfare History Network

MEDIA MONDAY: U-Boat sinks Schooner in the First World War (1917) - Hudson River Maritime Museum

Sea Wolves Unleashed – Inside Germany's First U-Boat War