KIMS Periscope No. 301
Mine Warfare at Sea in a Korea Contingency
미국 해군대학 교수
Raul (Pete) Pedrozo
Although sea mines have been effectively used both offensively and defensively in every major maritime conflict since the Russo-Japanese War (1904-1905), few navies have paid adequate attention to mine warfare until a crisis occurred. The most recent example is the Russia-Ukraine conflict, where there are reports that over 400 floating sea mines have significantly disrupted commercial shipping in the western half of the Black Sea. Given its successful use of naval mines during the Korean War (1950-1953), North Korea will likely employ this method of warfare in any future conflict on the Korean Peninsula.
Naval mines are self-contained explosive devices placed in the water to destroy enemy surface ships or submarines. They can also be used to deny enemy forces access to specific areas or channelize the enemy into specific areas. Types of sea mines include—drifting/floating mines (move with the current), moored mines (free to move within the limits permitted by the anchor attached to the mine), bottom mines (not intended to move), submarine launched mobile mines, and rising/rocket mines. Sea mines also detonate in different ways. They may be contact mines (which require contact with a vessel before they explode), influence mines (which are detonated magnetically, acoustically, or with pressure by the presence of a ship), or controlled mines (which are detonated from a shore station).
Naval mines can be employed for area denial, coastal and harbor defense, and naval blockade, as well as for anti-surface and anti-submarine warfare. Given their relative low-cost and tactical, operational, and strategic value, sea mines remain a weapon of choice for smaller states like North Korea to offset the technical superiority of an opposing naval force. These compact, easy to stockpile, highly durable, low maintenance set-and-forget weapons serve as a force multiplier, allowing manned platforms that would otherwise be engaged in missions such as blockade and maritime interdiction to be used for other tasks. As an inexpensive and effective anti-access weapon, naval mines provide less-capable navies like North Korea an asymmetrical capability to disrupt an enemy’s maritime operations that can alter the strategic landscape of an international armed conflict (IAC) at sea. To the extent they are employed consistent with the law of naval warfare, sea mines are lawful weapons.
Following the successful amphibious assault on Inchon by United Nations (UN) forces on September 10, 1950, General Douglas MacArthur ordered a second assault on Wonsan on North Korea’s east coast—D-Day was set for October 20, 1950. Although North Korean forces had started minelaying operations at Inchon, they were too late to stop the UN assault. Nonetheless, after the fall of Inchon, North Korean mining operations intensified around the Peninsula, which is well-suited for defensive mining operations. Most of the Korean coastline is shallow—favorable for sowing minefields—and comprised of muddy water, which offers excellent concealment for sea mines. Moreover, given the nature of ocean currents in the Yellow Sea and the Sea of Japan, floating mines launched in the north could travel the entire length of the peninsula in fifteen days.
The Wonsan minefield consisted of over 3,000 magnetic and contact mines spread over 400 square miles. The mines were laid over a period of three weeks using wooden barges equipped with iron or wooden tracks, capable of carrying ten to fifteen mines. After loading the mines by hand, the barges were towed out to sea where the mines were rolled off at 60- to 90-second intervals.
Minesweeping Task Group (TG) 95.6 began mine clearing operations at Wonsan on October 10, 1950. By October 25, only 225 of the 3,000 North Korean mines had been cleared. What was expected to be a five-day operation became a fifteen-day ordeal that resulted in a 10-day delay of D-Day for the Marine amphibious force. Assets available to Commander Naval Forces Far East to conduct the operation were limited to six Adjutant-class (AMS) minesweepers, four Admirable-class (AM) minesweepers, and twelve contracted Japanese minesweepers, compared to the 550-ship minesweeping fleet that operated in the Pacific during the Second World War. In a message to the Chief of Naval Operations, Commander, Task Force 95, Rear Admiral Allen “Hoke” Smith summarized the operation as follows: “The U.S. Navy has lost control of the seas in Korean waters to a nation without a Navy, using pre-World War I weapons, laid by vessels that were utilized at the time of the birth of Christ.”
The Korean War demonstrated that sea mines would be a weapon of choice in future naval wars. North Korean mines caused over 70 percent of all Navy casualties and sank the only four U.S. warships lost in combat. The Wonsan operation also resulted in a renewed focus on mine warfare, demonstrating that if the Navy cannot go where it wants to, when it wants to, it does not have command of the sea.
North Korea is currently estimated to have more than 50,000 ex-Soviet sea mines in its inventory. The U.S. Defense Intelligence Agency assesses that North Korea has a credible minelaying capability, using small surface ships to deliver mines to impede military and civilian shipping. North Korea will also likely use mines to defend against amphibious assaults, as it did at Wonsan, provide seaward flank protection for land forces, and defend strategic ports. Mine warfare has historically been instrumental in North Korea’s coastal defense and will remain a key component of its maritime defense strategy. It is also possible that North Korea may attempt to mine South Korean ports in the event of a conflict.
The Convention of 1907 Relative to the Laying of Automatic Submarine Mines (Hague VIII) is the only treaty that explicitly applies to the use of naval mines during an international armed conflict (IAC). Although Hague VIII only applies to automatic contact mines, most experts agree that the principles contained in the convention have become part of customary international law governing the use of all types of sea mines. Other rules governing mine warfare stem from related law of war treaties, general principles of the law of armed conflict (LOAC), and state practice.
Naval mines are lawful weapons and may be employed during an international armed conflict subject to certain restrictions. Unanchored automatic contact mines may not be laid unless they become harmless within one hour after loss of control over them (Hague VIII, art. 1.1). It is also unlawful to lay anchored automatic contact mines that do not become harmless as soon as they break loose from their moorings (Hague VIII, art. 1.2). Consistent with the general LOAC principle of distinction, belligerents may not lay mines off the coast and ports of the enemy with the sole object of intercepting commercial shipping (Hague VIII, art. 2). Mining for some other purpose, however, is not prohibited—e.g., mines can be used in the strategic blockade of enemy ports, coasts, and waterways, even if commercial shipping is incidentally affected.
Belligerents deploying mines must take every possible precaution for the security of peaceful shipping by providing international notification of the location of mine fields through official public announcements, communications to the United Nations, diplomatic notifications, or notices to mariners as soon as military exigencies permit. Belligerents must undertake to do their utmost to render automatic contact mines harmless within a limited time and, should they cease to be under surveillance, to notify the danger zones as soon as military exigencies permit. Notice addressed to ship owners will be communicated to governments through diplomatic channels (Hague VIII, art. 3). For example, a precautionary measure that a belligerent can apply to reduce risk of harm to neutral vessels is to warn neutral vessels that inadvertently venture near the minefield. Belligerents can also grant neutral ships safe passage through the minefield by providing a pilot or escorting the ship. The same rules and precautions apply to neutral States that lay automatic contact mines off their coasts (Hague VIII, art. 4).
Generally, belligerents must respect the sovereign right of neutral States and abstain, in neutral territory or waters, from engaging in acts that would constitute a violation of neutrality (Hague XIII, art. 1). Thus, any act of hostility (including mining) committed by a belligerent warship in the territorial sea of a neutral State is a violation of neutrality and strictly prohibited. (Hague XIII, art. 2). Thus, belligerents may not lay mines in neutral waters (e.g., internal waters and territorial sea).
Similarly, belligerents may not mine areas of indefinite extent beyond neutral waters.
The law of naval war is lex specialis and prevails over the peacetime law of the sea rules reflected in the United Nations Convention on the Law of the Sea (UNCLOS), but only to the extent that the two bodies of law are inconsistent. When conducting military operations in neutral exclusive economic zones or on the high seas, belligerents shall, consistent with military necessity and operational requirements, respect the rights and duties of neutral states. Accordingly, reasonably limited mined areas may be established provided neutral shipping retains an alternate route around or through the minefield with reasonable assurance of safety. Likewise, belligerents may not employ mines in a manner that denies neutral shipping transit passage of international straits or archipelagic sea lanes passage through archipelagic waters.
At the conclusion of hostilities, States have a duty to do their utmost to remove the mines they have laid. If one belligerent has laid anchored automatic contact mines off the coast of the other, the State that laid the mines must notify the other party of the location of the mines and each State must proceed without delay to remove the mines in its own waters. (Hague VIII, art.5). Thus, to ensure accurate notification and facilitate post-war removal or deactivation, the location of minefields must be carefully recorded.
North Korea is not a party to Hague VIII. Therefore, and given its unfortunate propensity to violate international rules and standards, it is questionable whether North Korea would comply with the customary rules of international law applicable to mine warfare. Nonetheless, the United States, South Korea, and other UN forces must prepare themselves to counter the formidable North Korean threat of 50,000-plus sea mines. Failure to do so will allow North Korea to use sea mines like they did at Wonson to deny freedom of maneuver to UN forces.
Currently, with only eight and thirteen mine warfare warships in their respective fleets, the United States and South Korea are ill-equipped to effectively deal with the North Korean threat. To address this capability gap, South Korean and U.S. forces have conducted an annual bilateral exercise—Clear Horizon—aimed at increasing capabilities and coordination between ships and aircraft in mine countermeasure operations. In 2016, Clear Horizon was expanded into a multilateral exercise to include Australia, Canada, New Zealand, and the United Kingdom to build a collective expertise in mine warfare. South Korean forces also conducted a multilateral mine countermeasure exercise with the Philippines and Thailand. These exercises are designed to practice procedures and tactics for mine-clearing operations and enhance interoperability between the participants’ mine countermeasure assets. Since 2016, Japan, South Africa, and Turkey have also participated in the multilateral exercise. These countries, which could one day be called on to support mine countermeasure operations near the Korean Peninsula, would add an additional 74 mine sweeping platforms and numerous aviation assets to the combined U.S.-South Korea mine warfare force. Unmanned maritime and aerial vehicles, such as the U.S. Navy’s Littoral Combat Ship Mission Modules (LCS MM) Program, can also be used to augment manned platforms to mitigate the impacts of sea mines on naval operations with reduced risk to personnel. The LCS MM Program consists of 48 unmanned surface vehicles that can perform both unmanned mine sweeping and remote mine hunting missions.
Despite modest efforts to narrow the gap in this crucial capability, the United States, South Korea, and Allies and Partners still find themselves unprepared to counter what could be a devastatingly effective North Korean mine-laying campaign. History has shown that such a course of action is entirely predictable – failure to adequately prepare for North Korea’s mine laying campaign will cause unacceptable risk to UN forces and could change the course of the conflict.
The author’s opinions expressed in this article are the author’s own and does not reflect the view of KIMS.