The Silent Service: The Law of Armed Conflict’s Blind Spots Regarding Modern Submarine Warfare
Submarines play a critical role in warfare due to their stealth, speed, endurance, and firepower. These attributes make them the “queens of the chessboard” in naval strategy and warfare. Modern submarines provide an array of unique capabilities, including strategic deterrence, intelligence gathering, anti-ship and anti-submarine warfare, land attacks, mine laying, and special operations support. Given the increasing vulnerability of surface ships to anti-ship weapons such as hypersonic missiles, torpedoes, unmanned underwater drones, cyberattacks, swarm tactics, naval mines, and space-based threats, submarines have become even more vital because of their inherent ability to remain undetected while being extraordinarily lethal and versatile.
Despite their strategic importance, the law of armed conflict (LOAC) regulating submarine operations remains underdeveloped. The U.S. Department of Defense Law of War Manual succinctly captures, in part, the consequences of this regulatory gap: “Although submarines must comply with the same law of war rules as surface ships, a law of war rule may apply differently in the context of submarine warfare because of the different circumstances of submarine warfare as compared to surface warfare” (§ 13.7.2). This post highlights one of the significant LOAC issues related to submarine warfare: the challenge of applying the principle of distinction to the use of torpedoes against modern surface warships or submarines.
Early Attempts to Regulate Submarine Warfare
The concept of underwater combat dates back to antiquity. A noteworthy milestone in submarine development was David Bushnell’s creation of the Turtle, a small one-person submarine to attack enemy warships during the American Revolutionary War. Before the First World War, the legality of submarine warfare was considered during the 1899 Hague Peace Conference. However, some States recognized the military importance of submarines and refused to agree to a prohibition (p. 105).
By the onset of the First World War, submarines had become a significant instrument of war. In 1914, Britain led the world in submarine power with 73 vessels, but it was Germany whose U-boats had the most substantial impact during the war, sinking over 5,000 allied and neutral ships totaling more than twelve million tons (p. 123). Britain, concerned about unrestricted submarine warfare and eager to protect its dominant position in surface warships and maritime trade, spearheaded efforts to ban submarines. These concerns were underscored, in part, by incidents such as the 1915 sinking of the RMS Lusitania by a German U-boat, which killed 1,198 people.
In the aftermath of the war, the world’s largest naval powers convened in Washington, D.C. to discuss naval disarmament and address rising tensions in East Asia. Ultimately, the Washington Naval Conference produced the 1922 Washington Treaty Relating to the Use of Submarines and Noxious Gases in Warfare. The treaty emphasized that submarines, like surface vessels, must adhere to established international law protecting neutrals and noncombatants at sea (art. 1(1) – (2)).
In 1930, Britain convened the London Naval Conference to build on the Washington Treaty’s efforts to regulate naval arms. The conference again debated banning submarines. The United States supported abolition, arguing that submarines “revolted the conscience of the world” and were inherently susceptible to misuse against merchant ships, violating established laws of war and principles of humanity (p. 107).
The resulting 1930 London Naval Treaty included Article 22, which stipulated: “Except in the case of persistent refusal to stop on being duly summoned, or of active resistance to visit or search, a warship, whether surface vessel or submarine, may not sink or render incapable of navigation a merchant vessel without having first placed passengers, crew, and ship’s papers in a place of safety.” A follow-up naval conference in London in 1936 confirmed the rules of submarine warfare outlined in the 1930 treaty through a procès-verbal.
The Second World War saw the rise of unrestricted submarine warfare in all theaters of operations. This included, but was not limited to, the German offensive during the Battle of the Atlantic, Japanese submarine strikes along the U.S. Pacific coast, intense submarine warfare in the Mediterranean involving Italy, Britain, and Germany, and the effective use of American submarines against Japan in the Pacific (p. 161).
Perhaps the most well-known war crimes prosecution involving unrestricted submarine warfare was against German Grand Admiral Karl Doenitz, who was the commander of the German U-boat fleet and then Commander in Chief of the German War Navy. In part, Doenitz was “charged with waging unrestricted submarine warfare contrary to the Naval Protocol of 1936 to which Germany acceded, and which reaffirmed the rules of submarine warfare laid down in the London Naval Agreement of 1930.” The International Military Tribunal at Nuremberg convicted Doenitz and sentenced him to 10 years in prison. Although the Tribunal convicted him of charges related to the German campaign of unrestricted submarine warfare, his sentence did not include any time for these charges
Treaties and State Practice Have Not Kept Up With Advances in Technology
There have been no new treaties specifically regulating submarine warfare since the interwar-era. Given the dearth of treaties on the law of naval warfare generally and on submarine warfare specifically, this area of law has relied on State practice as restated in LOAC manuals and soft-law instruments such as the San Remo Manual on International Law Applicable to Armed Conflicts at Sea and the Newport Manual on the Law of Naval Warfare. However, in the field of torpedo employment, there has been very little State practice to draw on since the conclusion of the Second World War.
What little State practice has occurred consists of three attacks at short range conducted against adversaries with limited anti-submarine capabilities. These include the 1971 sinking of the Indian frigate INS Khukri by a Pakistani submarine, the 1982 sinking of the Argentinian cruiser ARA General Belgrano by a Royal Navy submarine, and the 2010 sinking of the South Korean corvette ROKS Cheonan by a North Korean submarine. While all of the warships targeted by submarines in these attacks would be considered lawful military objectives under LOAC, two of these attacks nonetheless triggered widespread condemnation as possible war crimes (see here and here).
Little is known about the tactics of the North Korean submarine’s attack on Cheonan beyond the type of torpedo used. Reports about the tactics used to attack both the Khukri and the General Belgrano indicate that those attacks relied heavily on operations at periscope depth to identify and track the targeted warships. The HMS Conqueror went to periscope depth at least 5 times during the tracking of the General Belgrano, finally attacking from a range of 2,000 yards or 1 nautical mile. These are tactics that are largely indistinguishable from those used in the Second World War, when submarine commanders would visually sight targets while surfaced or at periscope depth, and then launch attacks from very short range (see this representative story about one American submarine commander’s tactics during the Second World War).
The relevance of this State practice for today’s submarine commanders engaged in a high-end conflict is limited. Since the Second World War, submarine and anti-submarine technology has evolved to the point where the tactics modern submarine commanders must rely on to survive and prevail look nothing like the tactics of their historical predecessors. Russian Udaloy class anti-submarine warships, for example, have a complex suite of sonar and radar capabilities for detecting submarines and an array of anti-submarine weapons that was inconceivable in the Second World War.
The primary threat to a Second World War submarine was being visually sighted and attacked with depth charges rolled off the deck of the ship or in some instances launched a short distance (100-250 yards) through the air. Udaloys, however, can much more readily detect submarines and then launch torpedoes, fire deck guns, and saturate an area with rocket-launched depth charges in a matter of seconds.
In parallel, the Udaloy class can dispatch anti-submarine helicopters armed with additional weapons (see this clip from the movie “Hunter Killer” to get an idea of what being on the receiving end of an attack from an anti-submarine capable warship might look like today). The fact that some depth charges and torpedoes can be fitted with nuclear warheads makes them an even more formidable threat. Using Second World War era tactics against such an adversary is a death-wish for a modern submarine commander, who is much more likely to be detected at periscope depth and virtually guaranteed to face a withering barrage of advanced weaponry within moments of being detected.
As a result of these technological advances in anti-submarine warfare, the modern submarine commander going up against highly-capable surface ships or submarines cannot rely on visual identification and short-range tactics in the same manner that typified the submarine tactics of the past. Unfortunately, the treaties governing submarine tactics are nearly a century old and limited in scope, and there is not sufficient State practice to draw on to make sense of how the LOAC principle of distinction applies in such engagements.
Unlike their Second World War predecessors, nuclear submarines spend almost all of their time submerged. Additionally, the anti-submarine warfare capabilities of peer surface fleets make it enormously risky for a submarine to use a periscope to visually confirm the identity of a potential surface target. Of course, if the target being prosecuted is another submarine, visual confirmation is not an option unless the submarine happens to be on the surface, which is not likely if the adversary is a nuclear submarine. This requires modern submarine commanders to shoot based on what they hear rather than what they see. How does a submarine commander who is shooting based on the noises around them satisfy the principle of distinction?
One might conclude from watching submarine movies that classifying another submarine is fairly straightforward. If one were to believe the classic movie “The Hunt For Red October,” a U.S. submarine just needs to listen for an adversary submarine crew to belt out the Soviet National Anthem to confirm the presence of an adversary submarine. This is a far cry from reality. The undersea environment is a noisy one, and it has become much noisier over the decades as shipping traffic has increased. Just since 1992, global maritime traffic has increased over 300 percent. Each one of these vessels makes noise, often a lot of it.
Making the problem harder is the omnipresence of marine life, which adds to overall noise levels. Without the benefit of eyesight, more information and more time is required to confirm the noise is what you think it is, the range of the target, and how close other potentially protected vessels are to the intended target. Resolving all of these questions is essential to satisfy the principle of distinction’s requirement to ensure that what is being attacked is a valid military objective vice a civilian ship.
So long as a submarine-launched torpedo hits a warship, there should not be any serious legal problems. However, considering that two of the three post-Second World War submarine attacks on warships still led to accusations of war crimes, one can anticipate the flurry of war crimes accusations that will be levied the moment a submarine commander inadvertently shoots a civilian ship without having visually verified the identity of their target. Modern submarine commanders are caught between outdated treaties and State practice on the one hand, and highly capable adversaries that require commanders to shoot more often based on sound alone and at extended ranges on the other.
Conclusion
This post merely scratches at the surface of the challenges of applying LOAC to modern submarine operations by pointing out the unique challenges of employing the principle of distinction to the use of torpedoes in modern submarine warfare. There are other questions worthy of inquiry including how to apply treaty restrictions on interwar torpedoes to modern torpedoes, to what degree the noise and presence of civilian shipping can be used to mask a submarine’s location, and so on. Submarines do not fight like any other class of ship. The most relevant treaties are nearly a century old and most State practice dates to the Second World War.
Military manuals do not adequately address this gap, beyond stating unhelpfully that the same laws apply to submarines as to surface ships. As technology continues to evolve and the nature of submarine warfare continues to change, it is critically important that the law of naval warfare catch up to address these emerging challenges and provide clear and practical standards for current and future submarine commanders.
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LCDR Christopher Hart is an assistant professor in the U.S. Naval Academy’s (USNA) Leadership, Ethics, and Law Department.
Brigadier General (ret.) David A. Wallace previously served as the Professor and Head of the Department of Law at the United States Military Academy, West Point, New York, and has been designated a Professor Emeritus. He is the United States Naval Academy Class of 1971 Distinguished Military Professor of Law & Leadership.
The views expressed in this work are those of the authors. They do not necessarily reflect the official policy or position of the United States Naval Academy, United States Military Academy, the Department of the Navy, the Department of the Army, or the Department of Defense.
Photo credit: U.S. Navy
