What will occur when the busiest oil chokepoint in the world is confronted by a submarine force that is made to blend in? Little has been told about the Iranian undersea fleet excepting as an appendix to missiles and fast boats, but the geometry and physics of the Persian Gulf is where the true value lies. The Strait of Hormuz directs shipping through narrow controlled lanes and the depth of the Gulf, the intensity of the current and the intense background noise generates underwater tracking as a miserable set. Such a setting reduces a diesel-electric submarine capable of halting, listening, and waiting to a “platform”, and transforms it into a moving section of ocean ground.
Iran continues to hold in inventory the most technically impressive boats the three Russian-built Kilo-derived submarines referred to locally as the Tareq class. Their length is approximately 74 meters, and they can carry 18 torpedoes, and they are usually linked to low acoustic signatures with the assistance of anechoic coating that may confuse sonar images. The snag is, geography: these submarines require a minimum of 164 feet of water to move, which limits them to much of the Persian Gulf and pushes their most natural hunting grounds into more complicated dives, like the Gulf of Oman and beyond. Despite that limitation, the presence of the Kilos places any navy functioning within the area under the constraint of having to consider extensive regions as areas of ambush and not passage.
Iranian smaller designs are the more custom-made to the shallow and littered littorals of the Gulf. Iran has made use of Fateh-class coastal submarines, whose dimensions measure approximately 48 meters and around 600 tons underwater, and which are capable of performing prolonged patrols in the region, but they have the heavyweight torpedo armament and mine capabilities. They do not just have tactical value but also an industrial one: the Fateh line is commonly discussed as a sign that Iran is able to repeat the practice of building their own submarines and not be dependent on the imported hull. Another novel feature of the Fateh shown by Iran is an air-independent propulsion (AIP) plug, which is used to increase the underwater range, a significant advantage in particular when snorkeling is possible and the submarine seems most vulnerable.
However, the boat that most fits into the logic of close quarters offered by the Strait is the midget submarine. The Ghadir-type of built-in-mass Iranian ships, which have North Korean ancestry, tips into the acoustic anarchy of the Gulf. Small submarines are able to take advantage of rocky bottom outline and coastal noises and they are capable of waiting where large boats are unable to safely navigate. The concept of operation is simple; force escorts and patrol airplanes take time and dedication to disprove threats in waters where a guarantee is costly.
This is where the “black hole” mystique of Iran is related to a larger, stratified denial policy. Submarines are not working alone, they are used in conjunction with mines, land based weapons against ships and fast attack crafts. The net impact of these is to ensure that routine maritime security operations such as an escort mission, clearing and verifying missions all consume a disproportionate amount of resources. In the Strait of Hormuz, where traffic is bound to a well-organized scheme of separation, predictable routes lead to a greater utility of a submarine lying awake and listening. According to ISW, that is what is referred to as constraint moving ships through narrow Sea Lines of Communication; the very type of geometry that undersea ambush doctrine is designed to take advantage of.
Iran also demonstrated the desire in very high-speed torpedoes such as the Hoot, which is a super-cavitating design with a speed in excess of two hundred miles per hour. It is not the issue that these weapons might become a regular part of effective combat on the real-world battlefield but rather the planning overhead created by them: defenders must also consider the potential for short-warning conflicts on limited waters.
To navies charged with ensuring the sea traffic in the region is flowing, the strategic issue is not an Iranian submarine that is perfect. It is the cumulative indecision produced by several categories of boats, large boats that went to greater depth, medium boats that were designed to travel long distances and cover a larger geographical area, and midgets that had been designed to ambush in the shallows..
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