Mines come in two primary categories, moored and bottom mines, and in two types determined by their method of detonation, contact or influence mines. Contact mines detonate when the target makes contact with it, while influence mines are detonated by the target's influence on the surrounding maritime environment (e.g., its effect on the local magnetic field, sound, or pressure waves generated by the target's movement). Moored mines are tethered to a casing resting on the seafloor. Bottom mines lie directly on the seafloor. Moored mines can be either contact or influence detonated, while all bottom mines are by influence only.
Laying mines is a relatively simple process. Almost any kind of platform (surface ship, submarine, or aircraft) can lay mines. When Iran laid mines in the Persian Gulf in the late 1980s, for example, it used a wide variety of innocuous surface craft, including small dhows (wooden cargo ships) that were indigenous to those waters. The Iranians' purpose was to conceal mining operations from both their enemies and the international community that had condemned their use. It took the U.S. capture of an Iranian minelayer to prove Iran's clandestine activities. That incident constitutes the basis for one of the concerns of the late and post–Cold War era: terrorist employment of mines to attack shipping.
Unlike mine laying, mine countermeasures are complex and dangerous. Minesweeping is the oldest method, using ships that tow their countermeasure equipment through the area (field) where the mines are suspected or known to be. Minesweepers are constructed of nonferrous materials (wood, reinforced fiberglass, etc.) that use special propulsion systems and are heavily sound-dampened to reduce any influences that might detonate the mines they pass over. Since they precede their sweep gear, however, minesweeping can be a risky operation. The United States pioneered the use of minesweeping helicopters in the late 1970s. Besides being faster and safer than ships, helicopters and their equipment were air transportable, providing greater strategic mobility.
However, the Cold War era was marked by the development of increasingly complex bottom influence mines designed to defeat most minesweeping tactics. By the 1970s, they could be set for specific target types (e.g., cargo ships or aircraft carriers instead of destroyers). Some had counters that allowed a preset number of targets to pass before detonating. Others came with preset activation and deactivation dates, either to ensure safe passage during those periods, to establish a sanitation date, or to complicate mine countermeasures. The best mines combined all of these elements and usually required multiple influences to detonate. Defeating these mines necessitated extensive sweeping over several weeks to provide a reasonable probability, but not certainty, of safe passage.
This technology forced a shift to mine hunting, using precision sonars and other sensors to hunt for mines. This is a particularly slow process, however. Although sensors can detect bottom mines, they also discover other objects of similar shape and dimensions. Moreover, tides, marine life, and bottom materials tend to obscure the mines over time. Hence, every suspected mine has to be investigated individually. Prior to the 1980s, most nations used divers to investigate suspected mines and disarmed those that they found. The inherent dangers involved with such operations inspired the West to investigate safer mine-hunting methods. The United States reportedly employed specially trained mine-hunting dolphins in Vietnam and the Persian Gulf, a method that remains controversial to this day. As the Cold War drew to a close, however, most Western nations, including the United States, relied increasingly on remote underwater robotic systems to detect mines.
Mine warfare figured prominently in four of the Cold War era's hot wars: the Korean War, the Vietnam War, the 1967 Arab-Israeli War, and the Iran-Iraq War. The Democratic People's Republic of Korea (DPRK, North Korea) laid thousands of mines off its coast following the 1950 Inchon landing. With America's mine countermeasure units long decommissioned after World War II, the United States reactivated the Imperial Japanese Navy minesweeping units, including their crews, to sweep the mines protecting Wonsan and Hangnam. Egypt also laid thousands of mines during the 1967 Arab-Israeli War to close the Suez Canal and Sharm El-Sheik. American mines completely closed Haiphong Harbor in the Democratic Republic of Vietnam (DRV, North Vietnam) and other ports to shipping in 1973. The agreement that ended the Vietnam War called for the United States to clear out the minefields, a process that took more than two months. Several months later, those same mine countermeasure units joined with Egyptian forces to conduct the mine clearing and salvage effort that reopened the Suez Canal after some eight years of closure. Mines were also a large concern during the 1991 Persian Gulf War.
Iranian-sponsored terrorist groups also resorted to the use of sea mines, laying moored contact mines off Lebanon's coast. Although not effective militarily, Iranian mines embarrassed the United States, nearly sinking the frigate USS Samuel B. Roberts on 14 April 1988. Lacking effective mine countermeasure units that could operate in the Persian Gulf, U.S. forces had to use the tankers they were escorting as ad hoc minesweepers. Two other U.S. Navy units were damaged by mines during the Persian Gulf War, driving the U.S. Navy to reinvest in new mine countermeasure technology.
Mines remain a major obstacle today. Their existence or suspected presence in a harbor or shipping lane can create an almost paralyzing effect on shipping. Defeating naval mines and, perhaps more importantly, identifying the perpetrators who laid them will be a critical naval mission well into the future. Carl O. Schuster
Hartmann, Gregory K. Weapons That Wait: Mine Warfare in the United States Navy. Annapolis, MD: U.S. Naval Institute, 1991.
Carl O. Schuster