Though the popular conception is that the Pacific was the home to the great naval conflicts of World War II, the Atlantic was by far the most important theater of ship engagements. The powers that controlled the sea lanes would control the land beyond it — if the Allies wanted to penetrate Fortress Europa, they would need to take control of the seas that surrounded it first. The majority of the surface action in the Atlantic and surrounding waters took place from the onset of the war through the end of 1942. The naval war from this point, though not over until after D-Day, was fought mainly between U-Boats and Allied convoys. The entire war can be broken down into seven periods:

September 1939 - May 1940

Phase One saw some of the more impressive battles of the war, including the sinking of the Courageous and Royal Oak, as well as the Admiral Graf Spee. The loss of the Graf Spee was a bad omen for the German navy, but the successes of the U-Boats throughout this period promised to keep it a close fight. The end of Phase One comes with the defeat of France. Germany now had naval bases along the Atlantic (France) and the North Sea (Norway) — a serious threat to the Great Britain. Germany’s Prize Ordinance called for U-Boats to stop all enemy or neutral shipping and search for any war supplies. It was set in place to avoid direct confrontation, as had been policy in World War One. Knowing that this policy drew the U. S. into the first war, the Prize Ordinance was meant to deter overly anxious submarine captains by restricting their options. By the end of Phase One, however, U-Boats were freely attacking enemy shipping without reservation.

June 1940 - May 1941

The second phase of the war was one dominated by the Axis powers. Italy declared war on France and Britain 10 June 1940, which dealt a serious blow to English convoy action throughout the Mediterranean. The freedom the German U-Boats now enjoyed with their multitude of bases allowed wolf packs to wreak havoc to any shipping around the British Isles. It was clear that unless relief came to the British, the Kriegsmarine would dominate the Atlantic and seal Europe’s fate. In March of 1941, the United States passed the Lend-Lease act — 50 year old destroyers were given to Great Britain and the Allied cause in return for 99-year leases of naval bases in the Caribbean, Bahamas, and Canada. This infusion of new ships was enough to keep victory out of Axis hands. The phase came to an end with the sinking of the Bismarck in May of 1941 off of Denmark. At the same time, the Allies had made significant progress on breaking the German codes, especially through the capture of the U.110 submarine early in May of 1941. Code books and the German Enigma machine were now in the hands of the British, and the pride of the German navy was lying at the bottom of the North Sea.

June 1941 - December 1942

The next phase of the battle is one of a cat and mouse game, with each side remaining fairly equal. Though the entry of the U. S. into the war brought increased strength to the Allied navy, the German U-Boats kept their impact to a minimum. The introduction of RAF anti- submarine planes occasionally alleviated the pressure of the Axis forces.

January 1943 - May 1943

Rommel’s defeat in North Africa was key to the Allies in containing Axis expansion; to supply the effort nearly gave the Germans control of the Atlantic. As Allied ships were diverted to protect convoys in the Mediterranean, the Atlantic convoys were left with only minimal protection. In March of 1943, only 30% of Allied ships reached port safely. With over 100 U-Boats in the waters of the North Sea and Atlantic, this danger can be easily understood. Victory in Africa brought relief to the Atlantic convoys — but the true end of this phase was the withdrawal of the majority of the U-Boats for refitting and upgrading to their German ports.

June 1943 - August 1943

As the majority of the German U-Boats were in dock for upgrades, the Allies began a concentrated air campaign to destroy submarines off the coasts of Britain and France. The German response was to equip U-Boats hastily with AA armament and send out Ju88’s to deal with Allied attacks — neither were successful.

September 1943 - May 1944

The upgraded U-Boats returned to service, armed with new homing torpedoes, improved radar detection, and the schorchel air mast (this device allowed for the submarines to recharge their batteries while running submerged). In spite of the advanced new U-Boats, the tide had shifted to the Allies. The German navy lost her two last great battleships — the Tirpitz and Scharnhorst during this time, as the British navy had time to recoup during the absence of the full U-Boat fleet. It was during this time that the Germans began work on the next generation of U-Boats — the Type XXI and type XXIII, as well as the Walther-engine Type XVII. These submarines would have most likely returned control to the Germans, if it were not for the fact that Italy had been defeated. With the Kriegsmarine forced to fight the Wermacht and Luftwaffe for increasingly scarce resources, material and support quickly faded.

June 1944 to War’s End

The final phase of the Atlantic war is crystallized in the D-Day invasion. Admiral Doenitz ordered all U-Boats to concentrate on cross- Channel activity in early June, but only four were able to reach their objectives due to a concentration of Allied air and sea power. With the Channel sealed, the Allies were free to land a massive invasion force; with the lack of access to the Atlantic, the sea war was effectively over for the Germans. Though limited U-Boat activity continued through 1945, resources and equipment became so scarce that members of the Luftwaffe were transferred to the U-Boat arm in order to provide personnel for the remaining ships. The credit for the British and American victory goes in part to planning and in part to resources. The determination of the Allied naval forces kept shipping lanes open in spite of the deadly U- Boats; the untapped resources the Americans brought both directly and through the Lend-Lease Act pumped up the British just enough to keep them alive. Save for the U-Boat wolf packs, the German navy was neutralized by the end of 1942. The heavy losses in Norway and the destruction of capital ships early on, meant an uphill war of attrition for the Germans who could not afford the resources to construct the P Class and H Class replacements. The Italian navy, though well equipped, was outnumbered by the British — and was no match for the air power it encountered. The true wild card for the war was the French navy. Her destruction by the Royal Navy prevented the Italians and Germans from creating a force that would have outnumbered and overwhelmed the British.