World War II Atlantic Naval Campaign: Undeclared Naval War (1939-41)

Figure 1.--America was unprepared for war. The Germans spent a decade preparing and the Japanese even longer. Of the different services, it was the Navy that did the best before the War with the very limited appropriations approved by Congress. And largely thanks to geography, it was the Navy was involved in the hooting war in the Atlantic even before Pearl Harbor and than after Pearl, it was the the Navy that took the brunt of the battle in the first year of the War. The Army and Army Air Corps had more time to prepare, the Navy was into it even before Pearl Harbor. And the Axis edge showed in the early engagements such as at Pearl Harbor and at Iron Bottom Sound in the Solomons. Ironically where the Axis faltered badly was in rapidly training new units after the War broke out. One might think that with so much experience that the Axis countries would have perfected the training process. Just the opposite occurred. The Axis never shifted from a long leisurly traimning program to effective short term training. 7The edge the Axis forces held at the onset of the War was gradually lost as the United States rapidly expanded and effectively trained huge military forces that were able to take on experienced Axis forces. Although not often mentioned, the effectiveness of allied training program was an important facyor in the War. It was responsible for the victory at Midway only 6 months into the War and with inferior aircraft. As a result, as the War wore on it was the Axis that was fielding not only inferior ships and aircraft, but poorly trained inexperienced personnel. This was evident by 1944 with the Great Marianas Turkey Shoot (June 1944). By which time the U.S. Submarine Force composed mostly of men whgo had been civilans at the time of Pearl Harbor proved themselves as the only sucessful submarine force of the War, destroying the Japanese Maru fleet. In Euroope, the Luftwaffe were reduced to using virtually untrained recruits to fight off mightly Allied air armadas. While this was especially true of the more technical branches (Navy and Army Air Corps), we also see this with the Army. After the disaster at Kasarine (February 1943), the fledgling U.S. Army developed the capability of going toe to toe with their much more experienced abd ioften better armed German opponents.

Almost from the beginning of war in Europe, President Roosevelt began what was to become an undeclared war with Germany in the North Atlantic. The first tenative step was naval patrols to to prevent belligerent ships from U.S. waters. Also he began to think about bases in Bermuda and the Caribbean only days after the war had begun. While America would not enter the War until December 1941, Britain had an ally in the Atlantic almost from the beginning of the War. At first the American role was limited, but as the situation worsend and the German's expanded the U-boat fleet, the American role expanded. The Royal Navy was ill prepared for the war. Lossess to the u-boats were severe, despite the fact the Keiegsmarine began the War with only a small force. Months before American entered the War, the U.S. Navy was involved in a full-scale shooting war to protect the convoys needed to keep Britin in the War. The American public was not fully aware of the extent to which the Navy was involved. The American effort, however, played a major role in allowing Britain to to survive the NAZI onslaught. Hitler was enranged with America's clear violation of its neutral status, but ordered the U-boat commanders to avoid incidents with the Americans until the campaign in the East had been successfully completed.

War in Europe

Germany invaded Poland (September 1. 1939). The British and French still clinging to hopes fror peace demanded the Germans withdraw from Poland. When they did not, Britain and France declared war (Septembr 3). Both the Royal Navy and the Kreigmarine had war plans. The Germans immediately scored siome high profile victories, largely because the British were unprepared for war. The Royal Navy that began Word War II was a much shrunken force from World War I. Döneitz dis not, however, have the force needed to take advantage of British unpreparadness. Almost from the beginning of war in Europe, President Roosevelt began what was to become an undeclared war with Germany in the North Atlantic. His ininitial actions, because of the Neutrality Acts were very limited.

American Neutrality Laws

At the outbreak of war, American neutalitiy laws prohibited the sale of arms one the President had identified beligerant states. The principal law was passed in 1935. These laws were enacted because it was the protection of American shipping carrying supplies to the Allies was what was the rationale for entering World War I. The President delineated the combat zone in which American ships were prohibited from entering (November 4, 1939). The Roosevelt Administration worked to remove the prohibition on sales so arms could be sold to the Allies, but only on a cost and carry basis. The prohibition on carrying war supplies on American flag shops remained. It was at this time that the dministration engineered the registration of U.S. ships in Panaama, the beginning of flag of convenience regustrations.

Isolationist Movement

With the outbreak of war in Europe, the overwealming attitude of Americans was that this time the United states should stay out of the War. As President Roosevelt began working to repeal the Neutrality Acts, aid the Allies, and rearm, a power ful Isolationist Movement began to organize to oppose the Adminisdtrations actions. The Isolationists significantly impaired Rossovelts's ability to aid the Allies. Notable Americans like Henry Ford and Charles Lindberg played a major role in the movement. The Republican minority in Congress were strongly influenced by the Isolationists as were members of President Roosevelt's own Democratic Party.

First Steps (September 1939)

The first tenative step taken by the U.S. Navy was patrols to prevent belligerent ships from entering U.S. waters. Also he began to think about bases in Bermuda and the Caribbean only days after the war had begun. [Freidel, p. 323.] While America would not enter the War until December 1941, Britain had an ally in the Atlantic almost from the beginning of the War. At first the American role was limited, but as the situation worsend and the German's expanded the U-boat fleet, the American role expanded. President Roosevelt was disappointed with how long it took to organize naval patrols. There was large area to be covered and the number of patrol vessels was inadequate. There were, however, no U-boat attacks. The German U-boats at the beginning of the War had limited range. Hitler at any rate had no desire to draw America into the War and made this clear to Grand Admiral Erich Raeder, Commander of the Kriegsmarine. [Freidel, pp. 323-324.] After Poland, his goal was to negotiate a peace or defeat Britain and France.

Royal Navy

The Royal Navy was ill prepared for the war. The Government had substabtially reduced the size of the fleet. In paricularly the Naval planners had underestimated the effectiveness of U-boats.


The Keiegsmarine began the War with only a small force. Hitler had told naval commzanders that war would not cone until the 1940s and the naval war plan was based on this. Hitler allocated fewer resources to the Navy. AQnd those provided were poorly used. The Naval high command wanted large surface ships, somethj\hing Hitler agreed with. Only after the War began andc the effectiveness of the U-boats were demonstrated were substantisl resources allocated to U-boat constrution.

German Restraint

Hitler howed considerable restraint in the North Atlantic during the first 2 years of the War. The Kriegs Marinw wanted to launch an unrestricted commerce war against Britain. Hitler fully aware of it was just such a campaign that brought America into World War I, reacted cautiously. He appears to have been primarily concerned with keeping America out of the War as long as possible. Hitler rejected the initial Kriegsmarine plan for unrestricted sunmarine warfare (October 1939). He then ordered that American ships entering the combat zone should not be targeted (December 1939). The Kreiegsmarine wanted to begin alunching attacks off Halifax where mercants vessels were assembling to be formed into convoys. Hitler out of concern over the impact on American opinion if attacks were launched so close to U.S. waters, reject the request (February 1940). Hitler then issued very strict prohibitions on attacking American shipping anywhere in the Atantic (March 5, 1940). These restrictions were only slightly adjusted after the Western Offensive was launched (May 10, 1940). U-boat commandrs were permitted to attack American shipping trying to reach the British and French, but only if they were in the WAr Zone President Roosevely himself had earlier deleniated.

American Yachts

The Royal Canadian Navy virtually did not exist at the beginning of World War II. Therewere 10 effective ships. The Germans gave some thought to seizing the French island in the Gulf of St. Lawrence. The British Security operation swung into action and began sebding Candadian officials south to buy American luxury yachts caple of highseas operations. They wer converted to patrol vessels. They managed to but 13 before Amerucan Customs because of the Neutrality Acts stopped the sales. President Roosevelt intervened to get a 14th yacht to Canada. Canadian patrol craft, especually the Flower Corvetts were small, very basic ships. The Canadian sailorsaboard the American yachts had in comparison sumtuous quarters. U-boat captains reported a sudden increase in Canadian patrol activities. [Stevenson, p. 245-46.] This was the humble beginning of a massive expansion of the Candin Navy which would play a key role in the Battle od the Atlabtic.

Greenland (May 1940)

Grenland at the beginning of World war II was a Danish possession. And thus like Denmark was neutral. The NAZIs invaded and occupied Denmark (April 1940). Danish authorities on Greenland asked for American protection. The Danish ambassador submitted the request (May 1940). It was an early step in the undeclared naval war in the North Atlantic before America entered the War. Greenland unlike Iceland was not on the major sealances connecting America and Britain. Thus the huge island did not play a major role in the War, but wearher stations there were very useful to the Allies and would later play an important role in the success of D-Day.

Merchant Vessel Losses

Lossess to the U-boats were severe. The passage of Lend Lease (Match 1941) would count for little if the U'boats blocked the sea lanes. The Luftwaffe shifted its raids from London to major British ports. Hitler extended the War Zone to the eastern coast of Greenland (March 25). Churchill pleaded with Roosevelt to extend the U.S. neutrality zone easward to extend the range of U.S. Navy convoy escorts.

President Roosevelt

The President hoped that the British and French with American industrial support could defeat Hitler, but aftervthe fall of France it was obvious that Germany could not be defeated unless America entered the War. Most historians believe that President Roosevelt hoped to involve Ameica in the war against NAZI Germany and that he was merely waiting for an incident that he could use to justify a declaration of war. This may well be the case, but there is no documented evidence of it. The President did not reveal any such plans even to his closest advisers like Harry Hopkins. The first opportunity to expand the American involvement came when a German U-boat stopped and sunk the SS Robin Moor wgich was en route to Capetown and was not carrying war materials. (May 21). The British hoped for an American response, but Roosevelt took no action.

Bases for Destroyers (August 1940)

Churchill as the Panzers poured into France pleaded with President Rossevelt for assistance. One possibility was mothballed destroyers, sorely needed to protect the critical North Atlantic convoy routes. The U.S. Navy had "moth balled" 70 destroyers after World War I. In fact FDR as Assisstanat Secretary of the Navy had played a part in this. There were great dangers to America in providing these destroyers to Britain. Not only would it be an act only slightly short of war, but it would weaken the ability of America to rapidly expand its fleet. Even more serious was that if Britain capitualed, the destroyers might even fall into German hands. The President also faced political dangers in that the Republicans could charge him with weakening America's defenses, a serious concern in the middle of the 1940 presidential election campaign. FDR finally agreed on August 14 during the height of the Battle of Britain to provide the British badly needed destroyers for their Atlantic convoys being hard pressed by the U-boats. At this stage of the War any good news was extremely important for the British and Churchill. The executive order was issued August 27, 1940. The United States would trade 50 old Navy destroyers for 99 year leases on British sea and air bases in the Western Hemisphere (most were in the Caribbean and in Newfoundland). The approach was extremely savy politically. It sounded like an actual exchange and involved bases close to the United States. In actuality the British were more than willing to provide America bases. It was also a cold political calculation. It was still unclear as to whether Britain would survive. If there was to be a British Vichy, it would be important to have American bases on the British Atlantic and Caribbean islands. The President also allowed British pilots to train in the United States and British ships to be repaired in U.S. ports. The Flight Ferry Command and Eagle Squadron were created. These were very bold exactions taken by the President without Congressional cover in the middle of the presidential election campaign.

Directional Finding

Admiral Dönitz after the fall of France (June 1940) quickly transferred his headquartrs to l'Orient on the Bay of Biscay and conducted the Battle of the Atlantic from there. The key to his success wa in collcting infiormation on British convoys from various sources and then vectoring hus U-boats to those locations who would then strike as Wolf Packs. Secure radio communications using the Enigma machines waa key to their success. Radio communications were, however, a potentuak weakness, The British began exploting this success from the beggining of the War, three years before the Naval Enigma was solved. The initial effort involved directional finding. Fixes on U-boat transmussions picked up by two receiving stations could locate a-boat. At first the British were limited to their own receuving stations. The Federal Communications Commissiin (FCC) had a small surveilance unit, the Radio Intelligence Division (RID). It was assigned the job of finding unlicensed broadcasters. With the appearance of NAZI spies in America, President Roosevelt authorized the expansuion of the RID and appropriations to purchase modern equipment. Thus the United States had an extensive network of land based receiving stations which cold receive signals from Europe or ships at sea. Er are not sure when, but the RID began passing on information to the Britis\h Security Commission (DSC) in New York. The United States also developed a Huffduff (high-frequency-directional-finding, HF/DF). The control headquarters in Maryland passed hits on to Navy communications headquarters in Washington, D.C. [Stevenson, p. 247.] We are not sure when the RID and the U.S. Navy began sharing this information with the British, but we know that a system was in place during the hunt durung the hunt for Bismarck (March 1941).

Coast Guard Survivor Patrols

The United States deployed Coast Guard cutters in the North Atlantic for weather reporting duties. These missions went as far as the Bay of Biscay, hotly contested waters in the Battle of Biscay. The weather reporting ws aciver story. Weather in the North Atlantic mpves from west to East. Their real assignment was to search for survivors of U-boat attacks and report the locations of German ships and U-boats. The location near the Bay of Biscay was no accidebt. This wa waters the U-boats had to pass thriugh when leaving and returning to French ports and where theu were vulnerable to British air attacks. We are not sure when these patrols began. The USCG cutters also reported sitings of and radio fixes on German ships and U-boats. One such ship was the cutter Modoc near the Bay of Biscay. [Stevenson, p 239-40.] This obviously had nothing to do with guarding the U.S. coast. which spotted Bismarck and got off a signal (March 1941). This gave the British and idea as to wear to vector the Catlina PBYs they obtained from the United States.

Providing Catalina PBYs and Crews

The United States 'lent' British Coastal Command a number of Catalina PBYs. The British had nothing like them. They were at the time the longest range patrol craft available. We are not sure when the first PBYs reached Britain. This in itself did not violate U.S. law, but the Navy also provided advanced radioequipment and experiebced crews, obstensibly for training. This did violate the law. The PBY sent to search for Bismarck was piloted by USN Ensign Leonard from a base in Londonderry. The crew was mixed including Brits and other Americans. Smith and his crew had trouble finding Bismarck in overcast weather so he came down and as they came out of the clouds found themnselves flying straight at Bismarck which began blasting away at the PBY. [Stevenson, p. 240.] But the fearsome German ship was now located and permitted the Royal Navy to get off an air strike before it reached the protection of Luftwaffe air cover fom French bases.

Operation Barbarossa (June 22, 1941)

It was Hitler's invasion of the Soviet Union that brought American actiin. President Roosevelt ordered the Navy to begin escoring convoys as far as Iceland and to transfer ships from the Pacifi to the Atlantic Fleet to protect the North Atlantic shipping lanes. Increasing tensions in the Pacific prevented the actual transfer. Even so, this was a important step as it freed up Royal Navy escorts for deployment in homewaters against the U-boats. At this time, President Roosevelt explained to his advisers that despite the extension of the neutrality zone, the United States would not declare war unless thecGermans attacked American ships. The President also decided that he needed to meet wuith Churchill and instructed Hopkins to go to London to make the needed arrangements.

U.S. Navy: Shooting War

Months before American entered the War, the U.S. Navy was involved in a full-scale shooting war to protect the convoys needed to keep Britin in the War. This began with the Greer which participated with the British in an attack on a U-boat southwest of Iceland in the American neutrality zone. After the Greer dropped depth charges, the U-boat fired torpedoes. President Roosevelt declared German U-boatrs the "rattlesnakes of the Atlantic and stated that there very presence in the neutrality zone was an attack on the United States. He then ordered the U.S. Navy to protect American and foreign ships in convoys and to attack U-boats in the neutrality zone on site. This was a virtual declaraion of war, but Hitler fully occupied in the Soviet Union wanted for the time to avoid war with America. The destroyer USS Kearney (DD-432) was assigned to escort convoy ON-24 out of Iceland. U-boats found and attacked convoy SC-48. The Kearney joined in the defense of convoy SC-48. A Wolfpack of 13 U-Boats pressed the attack southwest of Iceland. A U-boat torpeoded Kearney which is severely damaged, but not sunk (October 17, 1941). There are 11 fatalities. The Kearney managed to get back to Iceland for repairs. A U-boat torpedoed and sank the U.S. merchant ship USS Lehigh off West Africa (October 19). A U-boat torpeoded the oiler USS Salinas (AO-19) 700 miles east of Newfoundland (October 30). Although damaged, there are no casualties and the ship reached port. U-boats torpedoed the destroyer USS Ruben James (DD-245) which sank west of Iceland (October 31). There were 115 men lot. Ruben James was the first U.S. Naval vessel sunk as a result of enemy action in World War II.

Public Knowledge

The American public was not fully aware of the extent to which the Navy was involved in a shooting war in the North Atlantic. Even the Isolationists who would have used knowkledge of the Administration's growing involvement were not fully aware. Part of the reason for this was that the sailors involved in these operations, such as the PBY crew that helped find Bismarck did not talk to the press. And for some reasom the press does not seem o have been overly inquisitive. Some of these actions were clear vilations of the Neutrality Acts and the Navy men involved could have been procecuted. An imprachment trial of the President would hve been possible and Roosevelt was fully aware of the potntial danger. He put his oath to protect the Cobstiyution ahead of the part to obey it. After Oearl Harbor all these legal niceties became moot as the American people realised that the President had been right from the beginning.


The American effort, however, played a major role in allowing Britain to survive the NAZI onslaught.


Freidel, Frank. Franklin D. Roosevelt: Rendezuous with Destiny (Little Brown: Boston, 1990), 710p.

Stevenson, William. A Man Called Intrepid: The Secret War (Harcourt Brace Jovanovich: New York, 1976), 486p.


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Created: May 25, 2003
Last updated: 9:13 PM 5/3/2018