An often overlooked aspect of the Battle of the Atlantic is the use of convoys not just as a defensive formation but as offensive formations as well. Not just shields to protect the merchant vessels but as swords to kill the U-Boats. However, in either role the convoy system only worked well when the conditions had been set for it to operate effectively and it was actually used. For example at the start of America’s entry into the war, simple blackout procedures were not followed on the East Coast and the convoy system was not instituted resulting in the German U-boats having a “Happy Time” off the American coast sinking ships at will. Sometimes not even bothering with a torpedo, but surfacing and shooting up the hapless merchant vessel with their desk guns. 
As Churchill himself said, the Battle of the Atlantic was a war of pure attrition. There would be no “flaring battles and glittering achievements” only “statistics, diagrams and curves.”  To prosecute this battle the Allied pick Admiral Sir Max Horton, a British submariner, as Command and Chief the Western Approaches. As a submariner he could and did get inside German Admiral Doentiz’s decision loop and understand what options Doentitz had while directing the German side of the battle. Horton created and enforced a new training policy forcing escort groups to think and act as a team. He also created hunter-killer groups of ships that would be strategically place to cover many convoys and come to their aid when attack. Lastly, rather than avoid known wolf pack positions he directed his convoys into their teeth, to lure the Germans into attacking, and then use his new weapons to kill the Germans. 
The Allies technological advantage in new weapons and new intelligence gathering was what made Horton’s aggressive policy possible. HUFF/DUFF radio detection gear placed on ships and longer range aircraft to cover more and more of the ocean and find and kill the u-boats. As well as operational improvements such as a controlling “Tracking Room” in Canada aided in the defeat of the U-boats. 
 Dan Van der Vat, The Atlantic Campaign: World War II’s Great Struggle at Sea (New York: Harper and Row, Inc. 1988) 266-267.
 Winston Churchill, Memoirs of the Second World War: an abridgement of the six volumes of the Second World War (New York Houghton Mifflin, Inc, 1959) 410.
 Richard Overy, Why the Allies Won (New York: W. W. Norton and Co., Inc., 1996) 54-56.
 Gerhard Weinburg, A World At Arms: A Global History of World War II (New York, Cambridge University Press, 2005), 381.