In the course of events in the Atlantic alone , German U-boats sank Attack almost 5,000 ships with nearly 13 million gross register tonnage , losing Earnings_and_losses 178 boats and about 5,000 men in combat .

In essence , the Battle Hostile_encounter of the Atlantic was a tonnage war Hostile_encounter : the Allied struggle Resolve_problem to supply Supply Britain and the Axis attempt to stem Preventing_or_letting the flow of merchant shipping Sending that enabled Preventing_or_letting Britain to keep Temporary_stay fighting Hostile_encounter .