Iran can succeed at blocking the Straits of Hormuz
Despite the challenges of going up against the numerically and qualitatively superior U.S. Navy, Iran could successfully blockade the Straits of Hormuz with a combination of assymetric attacks and naval mines.
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In the event of conflict, Iran might use suicide boat attacks or lay mines in the Strait of Hormuz. In April 2006, Iran conducted naval maneuvers including test firings of what Iran claims are underwater torpedoes that can avoid detection, presumably for use against U.S. ships in the Persian Gulf, and a surface-to-sea radarevading missile launched from helicopters or combat aircraft . U.S. military officials said the claims might be an exaggeration, although it is conceivable that such tactics could result in heavy damage to U.S. ships in the event of conflict. The potential danger to U.S. ships was again in evidence in early January 2008 when five IRGC Navy small boats approached U.S. Navy ships in the Persian Gulf in what U.S. officials called a “provocative act” and were warned off without armed confrontation. Th e incident could have represented an Iranian attempt to determine whether “swarming” of U.S. ships could compensate for superior U.S. firepower.
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Since paying a very high price for confronting U.S. ships in the late 1980s, Iran has steadily shifted its naval warfare doctrine, capabilities and command structure from a surface fleet controlled by the traditional navy toward an unconventional force dominated by the IRGC. This redirected focus seeks to threaten U.S. interests and forces by disrupting shipping and creating prohibitive costs to U.S. naval units operating in-theater. This new approach also relies on the Iranian military’s relative strengths – large numbers of anti-ship mines, cruise missiles, and swarming high-speed patrol and light attack craft – to threaten tanker traffic, overwhelm individual U.S. and allied vessels, and deny access to the Iranian littoral. In an August 2002 U.S. simulation, this cost the United States unacceptable damage to a carrier strike group.103
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Iran is believed to possess at least 2,000 mines. By historical standards, this is not a large stockpile. For example, the British and Americans laid more than 70,000 mines in an effort to seal the North Sea against German U-boats in World War I, and the United States and the Soviet Union each stockpiled hundreds of thousands of mines during the Cold War. Nevertheless, even small numbers of mines have been able to halt surface traffic when their presence was known. In 1972 the United States immediately stopped all traffic in and out of North Vietnam’s Haiphong Harbor with an initial drop of only 36 acoustic-magnetic mines. In 1991 the Iraqis were able to discourage a U.S. amphibious invasion by laying only 1,000 mines off the Kuwaiti coast, 2 of which later hit but did not sink U.S. warships. In 1950 the North Koreans delayed the U.S. landing at Wonsan by laying only 3,000 mines across 50 square miles. As these examples show, mines derive much of their power from the fear they induce, which is often based more on the psychological effect of a lucky initial explosion than on rational calculations of risk.
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The general point is that it does not require great imagination to think Iran could lay several hundred mines in the gulf. If the above conditions prevailed, for example, Iran could lay a total of 693 mines. This is not an especially large number, but in such a conªned area with such heavy commercial traffic, it would not take long for a tanker to encounter a mine. The effects of the MDM-6 mine on a tanker are unknown, but given that these mines have both more sophisticated detonation mechanisms and ten times the charge of the mines that hobbled tankers in the 1980s, the threat to tanker traffic cannot be dismissed easily. If shipping companies—and their insurers—believed that large swaths of the channels and surrounding areas were deªnitely mined, and in some places with mines ten times as powerful as what was seen in the tankers wars, they likely would halt or reduce shipping. Most important, however, an Iranian mine warfare campaign against shipping would guarantee U.S. intervention, fulfilling Iran’s basic goal. The common assertion that 2,000 to 3,000 mines would be needed to close the strait may not take this potential Iranian objective into account.
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Iran’s limitations, such as the command and control and targeting challenges it would face in littoral warfare, are not often appreciated. But its strengths are often overlooked as well, such as the stocks of missiles and much more explosively powerful mines it has acquired since the tanker wars of the 1980s. Likewise, although the United States retains the world’s best conventional military, its past experiences hunting mobile targets from the air and conducting MCM operations in the littorals do not inspire confidence that confrontation in the strait would end quickly. The United States’ fleet defenses have never been tested in combat against an adversary with large numbers of cruise missiles, and the United States is in the midst of a major transition in its entire concept of MCM operations. Given these realities, sanguine assurances about the course and outcome of military conflict in the strait seem unjustified at best, and dangerous at worst. Most important, Iran does not have to seal the strait entirely to provoke U.S. intervention, and once that intervention begins, the potential for further military escalation is high. In particular, if the air and naval campaigns appear to be dragging on, the United States might be forced to consider holding hostage other targets in Iran or using ground forces. Either way, a significant and sustained increase in the price of oil would seem likely.
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Other analysts dismiss the notion that Iran would be capable of disrupting the strait. They argue that blocking the strait would be a pyrrhic strategy, considerably damaging Iran’s own economy while having a negligible affect on the United States. They also argue that the size, readiness and capabilities of Tehran’s armed forces would be insufficient to block the strait. But the history of naval blockades shows that nations in similar situations have successfully endured the economic effects, and Iran could resort to an asymmetric naval tactic called ’dispersed swarming’. Hundreds of small armed boats attacking one or two at a time from various directions could conceivably overwhelm a US carrier battle group. This tactic would make it difficult for the US Navy to detect and repel Iranian naval forces, providing Tehran a means of circumventing the limitations of its inferior navy.