The document discusses the Battle of the Atlantic during World War 2. It describes how Britain needed to secure its supply lines that Hitler tried to cut off by sinking ships. It discusses various naval tactics used by both sides, including the sinking of the HMS Hood and the implementation of convoys escorted by corvettes, destroyers, and minesweepers. Technology like ASDIC, depth charges, hedgehog mortars, and aircraft helped the Allies detect and destroy German U-boats. While the U-boats were initially successful, increased production from the US and evolving Allied countermeasures eventually drove the U-boats back and prevented Hitler from starving Britain.