United States Enters the Battle of the Atlantic Summary

  • Last updated on November 10, 2022

Prior to the United States’ official entry into World War II, U.S. naval forces began escorting Anglo-Canadian supply and passenger convoys across the North Atlantic in the face of German U-boat attacks. Several “short of war” engagements with U-boat forces during this period hastened the involvement of the United States in the war.

Summary of Event

Great Britain, being an island nation, has always depended on seafaring not only for its commerce but also its very survival. In the years immediately preceding the outbreak of World War II, Adolf Hitler, mindful of the critical role played by German submarines in harassing British shipping during World War I, focused the Reichsmarine’s attention on the production of new submarines Submarines . Although German submarine production had been specifically forbidden by the terms of the Treaty of Versailles Versailles, Treaty of (1919) , Hitler managed to subvert the treaty by having German-manufactured submarine parts shipped to the Netherlands (ostensibly for sale there) and then covertly reshipped to Germany, where the parts were stockpiled until needed in warehouses of the Deutsche Werke engineering firm in Kiel. Likewise, crews for the new submarines were covertly trained at the Ubootsabwehrschule (antisubmarine warfare school), also located in Kiel. [kw]United States Enters the Battle of the Atlantic (Mar. 1, 1941) [kw]Battle of the Atlantic, United States Enters the (Mar. 1, 1941) [kw]Atlantic, United States Enters the Battle of the (Mar. 1, 1941) World War II (1939-1945)[World War 02];naval battles World War II (1939-1945)[World War 02];early U.S. involvement Atlantic, Battle of the (1939-1945) World War II (1939-1945)[World War 02];naval battles World War II (1939-1945)[World War 02];early U.S. involvement Atlantic, Battle of the (1939-1945) [g]Europe;Mar. 1, 1941: United States Enters the Battle of the Atlantic[00160] [g]Atlantic;Mar. 1, 1941: United States Enters the Battle of the Atlantic[00160] [g]North Atlantic;Mar. 1, 1941: United States Enters the Battle of the Atlantic[00160] [c]World War II;Mar. 1, 1941: United States Enters the Battle of the Atlantic[00160] [c]Military history;Mar. 1, 1941: United States Enters the Battle of the Atlantic[00160] [c]Wars, uprisings, and civil unrest;Mar. 1, 1941: United States Enters the Battle of the Atlantic[00160] [c]Diplomacy and international relations;Mar. 1, 1941: United States Enters the Battle of the Atlantic[00160] Churchill, Winston [p]Churchill, Winston;World War II military leadership[World War 02 military] Dönitz, Karl Frost, L. H. Hitler, Adolf [p]Hitler, Adolf;naval policy Raeder, Erich

The most effective weapons system to emerge from the Atlantic conflict was the German U-boat U-boats[U boats] (Unterzeeboot) in its several variant designs. These U-boats operated alone or in wolf packs of up to fifteen. The U-boats of 1941, particularly the Type-VII boats operating in the North Atlantic in 1941, were considerably more capable than the coastal-type UB boats that had served in the Kaiserliche Marine of World War I, which were barely capable of submerging to a depth equal to their own length (40 meters, or 131 feet). In contrast, the Type-VIIBs, although relatively small (66.5 meters, or 218 feet, in length and 800 tons of approximate displacement) were fast, maneuverable boats with a top speed of 17.2 knots (8 knots submerged) and a surface range of 6,500 nautical miles.

Once the war’s hostilities began, Hitler set his naval commanders, Grand Admiral Erich Raeder and Rear-Admiral Karl Dönitz (who would later succeed Raeder as naval commander in chief), to the task of severing England’s mercantile and naval supply lines. This action would imperil not only Britain’s food supply but also Britain’s access to lend-lease Lend-Lease Act (1941)[Lend Lease Act] military goods being sent from the United States to assist England in its war effort.

Officers on the bridge of a destroyer watch for enemy submarines as they escort a convoy through the North Atlantic Ocean.

(Library of Congress)

Because neither the British nor their Canadian allies possessed sufficient warships to escort the numerous convoys World War II (1939-1945)[World War 02];transatlantic supply convoys Convoys, transatlantic along their entire routes, a partial escort system was adopted. Under this system convoys leaving Halifax in Canada or any of the U.S. eastern seaboard ports were typically escorted for a portion of their voyage across the Eastern Sea Frontier, as it was called in the United States. The critical middle portion of the convoy route, from the point where the initial support force of warships peeled off until a British escort was resumed in the western approaches to the British Isles, held the most danger. The convoys traveled and faced U-boat attacks in an area bordered by Greenland, Iceland, and the United Kingdom (the GIUK Gap). The area remains a critical one strategically.

The period beginning in June, 1940, and extending through the latter half of that year was an exceptionally favorable time for U-boat crews. During that first so-called “happy time” (as it was called by the Germans), more than two million tons of enemy shipping was sunk. U-boat wolf packs roamed relatively unmolested throughout the lightly defended Atlantic convoy routes, and by spring of 1941 the Atlantic conflict had begun to quicken in its intensity.

At this time as well, conferences between U.S. military chiefs of staff and their British counterparts led to an agreement known as the ABC-1 Staff Agreement ABC-1 Staff Agreement[ABC one Staff Agreement] , which outlined specific collaborations between the U.S. and the British militaries should the United States be drawn into war. One of the most significant of these points of collaboration was the U.S. Navy’s agreement to assume the primary responsibility for escorting transatlantic convoys bound for Britain. Thus, on March 1, 1941, a U.S. Naval Support Force dedicated to convoy escort duty for “the protection of shipping” was formally constituted, consisting of three destroyer squadrons and four patrol squadrons of Navy Catalina and Mariner seaplanes, along with suitable tenders. Though still not technically at war, the United States became enmeshed in operations that would lead inexorably to open conflict with Germany. It was not long before significant confrontations occurred.





Convinced of the strategic importance of Iceland as a site for naval and air stations in the event of war, U.S. admiral Harold Raynsford Stark Stark, Harold Raynsford ordered the destroyer Niblack Niblack (ship) to perform a preliminary reconnaissance of the island’s coast. On April 10, while nearing the Icelandic coast, Niblack was diverted to rescue several boatloads of survivors from a torpedoed Dutch freighter. As the seamen were being taken aboard, Niblack’s sonar operator reported a submerged contact, unidentified, apparently closing for an attack. Niblack promptly counterattacked with depth charges. Although no blood was drawn on either side, this engagement marks the first presumed engagement between U.S. and German forces of World War II. (The United States was not yet an official combatant.)

Prior to the Niblack incident several U-boat attacks already had been made against U.S. ships and passengers, most notably the SS Lehigh (sunk on October 19, 1940); the SS Zamzam, a neutral passenger ship of Egyptian registry sunk by a German raider (with the loss of more than one hundred U.S. citizens who were passengers); and the SS Robin Moor, Robin Moor (ship) a U.S. merchant ship (torpedoed off the coast of Brazil on May 21, 1941). The Robin Moor incident particularly inflamed the American public since it had not been carrying contraband war material, nor had it been operating in a war zone at the time of its sinking. Within days of the Robin Moor incident, nine ships of Convoy HX-126 (Halifax to the United Kingdom) carrying lend-lease goods to Britain, were sunk off the coast of Greenland. On May 27, the much vaunted German battleship Bismarck, Bismarck (ship) which had obliterated the British battle cruiser HMS Hood in the Denmark Straits with a single salvo from its massive deck guns, was itself lost in action against the combined power of the British navy and air force. These events clearly demonstrated German belligerence in the North Atlantic.

The situation finally came to a head on September 4, when, en route to Iceland, the U.S. destroyer Greer Greer (ship) (with Lieutenant Commander L. H. Frost at the helm) detected a German submarine, U-652, by sound contact. Three hours later the submarine turned toward the Greer and fired a torpedo, which the Greer evaded. The Greer counterattacked with depth charges but, after evading a second torpedo, lost contact with the U-boat and resumed course for Iceland. The Greer incident marked the beginning of a de facto state of war between the United States and Nazi Germany.


Although many Allied chroniclers of the lengthy Battle of the Atlantic have downplayed the German U-boats’ significance and effectiveness—presumably for nationalistic reasons—it remains the case that few branches of the Wehrmacht were as effective as Admiral Dönitz’s “grey wolves” in reducing the enemy nearly to submission. Most tellingly, British prime minister Winston Churchill once remarked that the only thing that really frightened him during the war was the U-boat peril. Later in the war, the Battle of the Atlantic would eventually be won by a combination of improved submarine-detection technology applied with improved antisubmarine tactics that coordinated naval air and surface forces in effective hunter-killer teams.

The U.S. Navy’s escorts of British and Canadian ships across the volatile North Atlantic in the wake of attacking German U-boats marked the start of the United States’s entry into World War II, an entry made official after Japan bombed Pearl Harbor in December, 1941, and after Germany declared war on the United States a few days later. World War II (1939-1945)[World War 02];naval battles World War II (1939-1945)[World War 02];early U.S. involvement Atlantic, Battle of the (1939-1945)

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Hague, Arnold. The Allied Convoy System, 1939-1945: Its Organization, Defence, and Operation. Annapolis, Md.: Naval Institute Press, 2000. Explores the workings of the convoy system provided by the Allies during World War II. A comprehensive work.
  • citation-type="booksimple"

    xlink:type="simple">Hickam, Homer H., Jr. Torpedo Junction: U-boat War off America’s East Coast, 1942. Annapolis, Md.: Naval Institute Press, 1996. A U.S. Navy research publication that examines German U-boat attacks off the coast of the Eastern United States in the early stages of World War II.
  • citation-type="booksimple"

    xlink:type="simple">Morison, Samuel Eliot. “The Battle of the Atlantic.” In History of United Sates Naval Operations in World War Two. Vol. 1. Edison, N.Y.: Castle Books, 1947-2001. This fifteen-volume set, written by a U.S. Navy duty officer and Harvard historian, presents a detailed history of World War II naval operations. Contains many charts, tables, and illustrations pertaining to tonnage losses, actions and battles, and so forth.
  • citation-type="booksimple"

    xlink:type="simple">Smith, Kevin. Conflict over Convoys: Anglo-American Logistics Diplomacy in the Second World War. New York: Cambridge University Press, 1996. A comprehensive overview of the role of the United States in securing British and Canadian shipping during World War II.
  • citation-type="booksimple"

    xlink:type="simple">Stern, Robert C. The Type-VII U-Boats. London: Arms and Armour Press/Cassell Group, 2002. A well-illustrated book with historical photographs and annotated engineering plans.
  • citation-type="booksimple"

    xlink:type="simple">Williamson, Gordon. Wolf Pack. Oxford, England: Osprey, 2005. Presents a detailed analysis of the complete U-boat weapons system, including boat types, operations, tactics, bases, crews, equipment, and related information. Well illustrated with numerous period photographs, drawings, and diagrams.

World War II: Pacific Theater

World War II: European Theater

Roosevelt Signs the Lend-Lease Act

Sinking of the German Battleship Bismarck

Bombing of Pearl Harbor

Canada Declares War on Japan

Germany and Italy Declare War on the United States

Second Battle of El Alamein

Operation Dragoon

Categories: History