Contact Us   |    Join   |    Donate


The submarine has presented the potential of being a decisive weapon for the country bold enough to seize its potential throughout the twentieth century. Since World War I, submarines have accounted for 10,000 ships destroyed -approximately 80 percent of all combat-related sinkings totalling 40 million tons. The effectiveness of submarine warfare has caused nations to attempt to control submarine operations, construction, and weapons loadout to forestall the effect a well trained and properly directed submarine force can have. Attempts to restrict wartime submarine operations early in a conflict, by the nation having the initial edge in submarine technology and force capabilities; however, have led to wasted opportunities to play an important — if not decisive role – in a conflict’s outcome.

The submarine was an unknown quantity prior to the First World War, although fear of underwater weapons dated back to the 18th century with the TUR1LE’s attack on HMS EAGLE.

Few naval leaders — let alone policymakers — saw the submarine as the effective commerce raider, warship destroyer, or shaper of policy it was to become in the First World War. The consensus was that commerce raiding — the future focus of the submarine’s mission during two global conflicts — would be conducted along traditional lines and in accordance with international laws. Merchantmen would be stopped, searched for contraband, and if the ship was taken, the crew sent to lifeboats prior to destruction. A small minority saw the submarine’s potential in guen-e de course warfare. Any concerns could be summed by Winston Churchill in 1913 when he stated, •or the greatest question {in the next conflict) is the use of submarines to sink merchant vessels, (but) I do not believe that this would ever be done by a civilized power.”

German submarine operations at the beginning of World War I appeared to validate judgments that the submarine would not play a major role. Although the German submarine force had some successes in 1914 such as the sinking of the ABOUKIR, HOGUE, and CRESSY in less than an hour, submarines had little impact on the war at sea or on policy ashore. Existing prize rules and procedures for search and seizure made submarine warfare a very inefficient means of commerce raiding. The Royal Navy maintained command of the sea, English merchantmen facilitated England’s long supply lines to its empire, and Germany was effectively blockaded by British control of the North Sea.

The stalemate on the Western Front in 1915 motivated Germany to change its position on submarine warfare. Trench warfare made a military breakthrough on land seem unlikely. The German Navy looked at the submarine as an alternate military means to challenge British superiority at sea and react to the blockade of German ports. Following Britain’s declaring the entire North Sea a war zone, Admiral von Tirpitz advocated an unrestricted U-boat campaign against Britain’s seaborne trade and commerce.

The decision to conduct an unrestricted submarine campaign had important policy implications. All Allied merchant ships would be destroyed, but neutral ships had to be put at risk because of the British practice of using false flags to protect its shipping. This forced Berlin to carefully weigh the military advantages of an unrestricted submarine warfare campaign against the potential of the United States entering the war as a result of U-Boat sinkings. After careful consideration, the Germans chose to escalate the war against seaborne commerce in March 1915 using a clearly defined, publicly announced war zone around England and Ireland, coupled with official warnings in the press of potential hazards.

The political impact of the first U-boat campaign; however, was highly negative in shaping German-American relations. The sinking of the passenger liner LUSITANIA in May 1915 with the loss of 125 American lives was followed in August by the loss of American life on the British steamer ARABIC. These incidents resulted in strong U.S. diplomatic and political protests — sufficient for Berlin to believe the United States might declare war. Strong protests from Washington convinced the Germans that maintaining a neutral United States, for the time being, outweighed any success the U-boats gained at sea. In a move to placate washington, Berlin placed liners off limits and shifted their U-boats to the Mediterranean — away from American shipping. Nevertheless, Berlin’s actions had little affect in erasing the American perception that Germany was fighting from a lower moral position than Great Britain and the Allies.

Initial U-boat efforts at cutting the Allied sea lines of communications were hindered because the Germans did not have sufficient U-boats available to conduct an effective campaign. At the outset of the 1915 campaign, the German Navy could only call on about twenty U-boats, or one tenth the number called for in a staff study to accomplish its mission.

Successes from the 1915 U-boat operations, however, gave the German Navy confidence in the capability of the U-boat service to cut England’s supply lines. The German Naval Staff in 1916 again called for a continuous economic war to be waged by submarines, using every available means and without restrictions that would cripple U-boat effectiveness. Led by Tirpitz, the naval staff believed that based on previous experience British resistance could be broken after six months by unrestricted submarine operations.

Berlin still was not ready to make full use of the submarine as a weapon because it feared the possible entry into the conflict by United States. The Kaiser ordered that submarine attacks without warning be made only on armed merchantmen within the German War Zone. Nevertheless, the U-boat campaign fueled British propaganda efforts and was providing motivation for the United States to officially join the Allies. In 1916, the French steamer SUSSEX was torpedoed with three Americans injured. Washington strongly protested the attack and threatened to break diplomatic relations. To defuse the situation, Berlin announced its “SUSSEX Pledge”. The pledge guaranteed that Germany would conduct submarine warfare in accordance with established prize laws and, with the subsequent resignation of Tirpitz, U-boats were shifted to attacking warships.

Inconsistencies and lack of focus greatly hindered the anticommerce campaign’s military effectiveness. Total unrestricted submarine warfare was contemplated by Berlin only as a last resort when the German government came to the realization in late 1916 that they were no closer to victory than in 1914 and were engaged in a losing war of attrition. After the indecisive Battle of Jutland, German leaders again saw the submarine as the one naval weapon that had the potential to tum the tide in their favor.

In a key policy act, Berlin announced renewed unrestricted submarine warfare in February 1917 and abrogated the 1916 SUSSEX Pledge. German-American relations quickly deteriorated, with Congress declaring war in April1917. Although this final U-boat campaign was not successful in bringing the British to their knees, it came dangerously close to succeeding. The final statistics show the Germans sank 5,234 ships totaling 12,185,832 tons of shipping, but peak losses only occurred in 1917 when the Gennans fully committed themselves to an unrestricted submarine campaign.

The effectiveness of the Gennan Submarine campaign was not lost on the Allies at the end of the war. In essence, the Allies forced on Germany a zero option Conn of arms control. The Peace Treaty stipulated that the German Navy would be greatly reduced and would have no submarines — all U-boats and salvage vessels would be surrendered and those in shipyards broken up.

The success the Gennans had with their U-boats had a further impact by motivating the Great Powers to explore limiting the numbers and capabilities of submarines. During the 1920s, the inter-war arms control efforts to control submarine warfare achieved some results.

  • The Washington Naval Treaty of 1922 successfully limited the size of the major power’s naval forces, but the British call for a total ban on submarines was rejected.
  • The Three Parties Conference in 1927 resulted in the United States, Great Britain, and Japan agreeing to submarine force parity by limiting their numbers to 60,000 total tons, and restricting individual submarines to 1800 tons displacement, a 5″ gun, and a 13 year lifetime.
  • The 1930 London Naval conference further refined the submarine force level limit at 57,000 total tons. France and Italy, however, did not participate.

Further attempts to control submarine warfare in the 1930s highlight the pitfalls, and outright dangers, present when arms control negotiations are not conducted pragmatically. In 1933, Berlin began its clandestine submarine program and by mid1934 had assembled the parts for its first 250 ton U-boat in Kiel.

The British recognized that Germany’s rearmament would occur and attempted to avoid an all-out naval arms race. Seeking to curb German naval growth, the 1934 Bilateral Naval Agreement was signed. This document restricted Germany to 35% of the Royal Navy’s Surface fleet — and 45% of its submarine strength. However, it allowed Berlin in “special circumstances”, to build its U-boat force to parity with the UK if another power built submarines above the treaty limit. Some attempts were made to control submarine force size, capability, and operations and levels somewhat above the 1927 and 1930 limits were established.

Included in the naval treaty setting limits at the 1935-36 conference was a special protocol banning unrestricted submarine warfare. This agreement was signed by 40 nations including Nazi Germany.

Britain’s technology edge might have influenced London to believe they could afford to allow Germany to start a small submarine force to avoid an unwanted arms race during severe economic times. An out-of-the-political-mainstream Winston Churchill saw the issue clearly.

“Great play was made by the British ministers with the Germans’ offer to cooperate with us to abolish the submarine. Considering the condition that all other states should agree at the same time, and there was not the slightest chance of the other countries agreeing, this was a safe offer for the Germans to make. Negotiations with the Germans (could be considered) as the acme of gullibility and that what had been done was to authorize the Germans to build at their utmost capacity for five or six years.”

Adolf Hitler’s submarine warfare policy did much to neutralize the U-boat early in the Second World War. German Prize Rules were laid out in the manner agreed in the Anglo-German naval conversations of 1935 – and in compliance with international law. Hitler’s policy quickly lost credibility in the first days of the war when the U-30 sunk the liner ATIIENIA –with the loss of American life. Nevertheless, Hitler maintained his policy of non-provocative submarine warfare by giving direct orders that passenger ships would not be attacked, even if escorted.

Even without policy restraints, it is doubtful that the small German submarine force could have cut Britain’s supply lines in 1939. Once again, Germany entered the war without sufficient numbers to make commerce raiding effective — only 57 U-boats were in commission. In addition, U-boats were involved in the support of German attacks on Northern and Western Europe.

Hitler shifted his naval strategy in 1940 when Germany was compelled to give up plans to invade England following the Battle of Britain. It did not seem likely that England would be defeated rapidly .and submarine warfare appeared to be the most expedient way to cut England’s sea lines of communication. In the fall of 1940, Hitler adopted the advice of Admiral Raeder and began a strikingly successful submarine campaign.

The U-boat strategy, however, was not without restrictions. Hitler continued to make a concerted effort to avoid drawing the United States into the war over the submarine issue. From the start of the war, German submarine commanders were instructed to avoid attacks on American ships at all costs. Indeed, the United States Congress cooperated in this effort by adopting the Cash and Carry Policy that prohibited American merchantmen from entering combat zones. As a result, submarine warfare did not emerge as the emotional issue to propel the United States into a European conflict.

Hitler, however, provided an excuse to further shift U.S. policy on March 25, 1941, by extending the German war zone to beyond Iceland. Roosevelt used Hitler’s expansion of European war zones to justify extending American Neutrality patrols from 300 miles off the U.S. coast to just west of Iceland. This decision began an undeclared war with Germany. Initially, U.S. warships only cooperated with the Royal Navy by supplying contact reports on U-boats. This situation escalated in August 1941 when a U-boat, essentially acting in self-defense, fired a torpedo at the USS GREER– actively assisting British ASW forces. The GREER Incident was quickly judged by Roosevelt as a deliberate attack and the President quickly authorized the U.S. Navy to use a “Shoot on Sight” policy against the “rattlesnakes of the Atlantic.” This policy also allowed U.S. warships to escort convoys to Iceland – giving the over-extended British ASW forces greatly needed support. These actions, however, were not without cost. U.S. naval forces soon discovered that the Germans could also shoot back as shown by the subsequent torpedoing of the USS KEARNEY and the sinking of the USS RUEBEN JAMES.

Berlin appeared to be holding fast to its policy of not provoking the United States to declare war– regardless of U.S. actions just short of war in the Atlantic. Restraints on the Uboat force prevented them from attacking convo~ off the U.S. coast and U-boat commanders were still under orders to avoid incidents with American vessels. Hitler was engaged in the invasion of the Soviet Union and appeared to want to avoid going to war with America at the height of the Russian campaign.

The restriction placed on the German submarine campaign might have been in keeping with a well thought out foreign policy of restraint had Hitler kept the United States a hostile neutral. Four days after Pearl Harbor, however, Hitler declared war on the United States for no urgent-or readily apparent-reason. It is possible that Roosevelt’s aggressive use of American ASW forces against the U-boats could have played a large role in Hitler’s decision to declare war.

Hitler’s declaration of war freed the U-boats from all policy restrictions. Tonnage sunk by the German submarine force dramatically rose in 1942 but German war aims would have been better served if these losses had occurred earlier in the conflict. The United States submarine force was never saddled with the type of policy restrictions in the Pacific that the German Uboats faced in the Atlantic. With the exception of avoiding attacks on neutral Soviet merchantmen in the Pacific, unrestricted submarine warfare was the official policy against Japan.

U.S. submarine warfare policy was militarily and politically sound; particularly against the backdrop of Japan’s surprise attack. It was an action that never would have been challenged by the American public. In addition, the U.S. unrestricted submarine warfare policy decision was handled in a very adroit manner. Strict secrecy was imposed on submarine operations to mask their operational effectiveness. The same secrecy, however, also served to avoid dealing with the issue of Germany being condemned for engaging in the same type warfare the United States was conducting with similar effectiveness and ruthlessness in the Far East.

The United States unrestricted submarine warfare campaign eventually proved to be a critical ingredient in Tokyo’s defeat. Despite being initially hindered by faulty torpedoes and concentration on fleet operations early in the war, U.S. submarines eventually severed Japan’s sea lines of communications.

The American submarine operations in the Pacific underscored the fact that technology made unrestricted submarine warfare a necessity for commerce raiding in hostile waters. Radar, sonar, aircraft, and convoys with their escorts, had advanced ASW techniques to the point where it would be virtual suicide for a submarine to operate in accordance with the existing rules of search and seizure. Nevertheless, Admirals Erich Raeder and Karl Doenitz, successively Commanders-inChief of the German Navy, were charged at the Nuremberg Tnbunal with war crimes surrounding Germany’s use of unrestricted submarine operations. These charges, however, were refuted by evidence at the trial – including testimony by Admiral Nimitz, Commander-in-Chief of U.S. naval Forces in the Pacific — that clearly proved the Nazis performed the same operations that the Allies did against the Japanese.

The Nuremberg Tribunal forced a change in the legal consequences of unrestricted submarine warfare in a total war. Its decisions, however, did little to legitimize unrestricted use of the submarine as a weapon of war in all circumstances. Conflicts fought since 1945 have presented opportunities to policymakers to make extensive use of the submarine, but with the exception of the Falkland Conflict, the submarine has played a limited operational role.

The Falkland Conflict illustrates that, in less than total war scenarios, the submarine may be viewed as a weapon of escalation subject to political restraint Prior to the arrival of their task force in the area, the British placed submarines in the area to enforce their blockade of the island but these submarines did not attack any Argentine supply ships.

The British policy reflected the perception that submarine attacks are not automatically considered legitimate acts of war — especially against merchantmen. In low-intensity politicomilitary situations, lethal submarine attacks on non-combatants would be out of place. To sink ships without warning — the only way submarines can operate effectively -would be fighting a war at a level out of step with the remainder of the international community.

The covert nature of submarine operations and its advanced command and control systems does allow the submarine to be a selective instrument of national policy. A sudden preemptive submarine attack can send a clear political and military message.

The HMS CONQUEROR’s sinking of the Argentine cruiser GENERAL BELGRANO well outside Britain’s announced 200 nautical mile exclusion zone clearly signaled the Argentine Junta of Prime Minister Margaret Thatcher’s resolve to do whatever was necessary to retake the Falklands. The attack clearly stated that hostile naval forces would be at risk from sudden attacks from unseen attack submarines. This reality removed the Argentine Navy as a factor for the remainder of the campaign.

Submarine warfare has significantly demonstrated the potential to influence the outcome of both major conflicts and limited wars. From conflicts involving submarines and the efforts to control submarine warfare the following salient points emerge:

  • The submarine offers a great military advantage to the country owning adequate numbers to pursue its policy and military objectives. The length of time required to construct a state-of-the-art submarine necessitates having sufficient number available at the start of a crisis.
  • Political restraints can delay the effect of the full force of submarine warfare to the point where the effect is negligible.
  • Sinking ships without warning remains an act of escalation to be employed selectively by the policymaker with care and restraint.
  • The Nuremberg Trials provided realistic guidelines dealing with the legality of submarine warfare but in the international community, unrestricted wartime submarine operations have not yet been legitimized.
  • Finally, submarine arms control and attempts to regulate submarine warfare have been difficult to accomplish .

Naval Submarine League

© 2022 Naval Submarine League