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

U-BOATS UNLEASHED ON EAST COAST SHIPPING - World War II Day by Day

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

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

How German U-Boats Were Used in WWI—And Perfected in WWII

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

If the Type XXI Uboat was manufactured earlier in WW2, would it have a profound impact on the course of WW2? - Quora

Kaiten - Warfare History Network

Operation Neptune

Wreckage of cargo ship sunk by German U-boat in WWI found at bottom of Irish Sea - Mirror Online

German WW1 U-Boat Campaign That Almost Broke UK

Battle of the Atlantic: Archaeology of an Underwater WWII Battlefield: Mission Logs: September 4: NOAA Office of Ocean Exploration and Research

The World Is Going Into The Red From The Red Sea Crisis

Red Sea conflict: Dozens of Canadian ships delayed