Swarming Small Surface Craft

During a ceremony on 28 May 2020, 112 new-generation offensive speed boats of different classes were unveiled and delivered to the naval forces of Iran’s Islamic Revolution Guards Corps (IRGC). Enjoying hydrodynamic functional features, the boats are capable of sailing at a high speed, with a low radar cross-section (RCS) and a high level of offensive power, the IRGC’s Sepah News reported.

The threat from small surface craft to the larger U.S. surface ships is illustrated by several incidents in the Persian Gulf and the Strait of Hormuz since the early 1980s. Asymmetrical naval warfare is a way to offset, deter, deny, mitigate and negate an enemy’s strengths by exploiting his vulnerabilities through surprise attacks, infiltrations, ambushes, hit-and-run tactics, indiscriminate harassment and swarming techniques. In addition, Iran must use CCD to decrease the situational awareness of the enemy. It must enhance the element of surprise as a core practice on all levels of war, and decentralize the fighting forces.

Swarming is a scheme of maneuver involving the convergent attack of several (or more) semiautonomous (or autonomous) units on a target force in some particular place. Swarming has occurred throughout military history, and the lessons of this past experience may offer insights into a possible future application of swarming. Very little historical research has been conducted on the use ofswarming, let alone a comprehensive review of swarming as a major theme within military history. Most examples of military swarming are tactical "Massed Swarm" cases from the ancient world and the Middle Ages, wherein a swarming army begins as a single massed body then disassembles and conducts a convergent attack.2 Other swarming examples are "Dispersed Swarm" cases, such as those drawn from the history of guerrilla warfare, wherein the swarming army is initially dispersed but then converges on the battlefield without ever forming a single mass.

Swarming is one of the current “buzzwords” of choice in Department of Defense circles. As with some buzzwords “swarming” is being a bit over-used. A key requirement for the swarm is to be able to strike at the target from different directions. There must be relatively large numbers of small attack craft that are well connected, from a communications or networked perspective as well as from a geographic or physical one.

The tactic that appears to have the most traction is that of ‘swarming’ attacks by large numbers of inshore attack craft. There is no readily definable criteria for these craft – they can be as small as recreational vehicles such Jetski’s and as large as a naval or coastal patrol fast patrol boats. Nor is there just one type of ‘swarming’ attack. Attacks can come from multiple axes. The navies of coalition nations have conducted numerous studies and analyses to begin to come to grips with dealing with the threat of swarming small boat attacks. In one study for the US Navy, an industry team found that different types of threat platforms had different effective weapons ranges. The study grouped these into two general categories; small threat platforms (cigarette boats, Boghammars and others) with a maximum effective weapon range from 0.1 to 0.5 nm and larger naval vessels such as advanced patrol boats carrying short-range guided missiles.

The terrorist attack on the guided missile destroyer USS Cole in Aden harbor in 2000 provided a devastating example of what a small group of terrorists can do to a modern warship with minimal resources--in the case of the USS Cole, two terrorists in a small boat carrying a few hundred pounds of explosives came close to sinking a billion dollar warship.

The success of the attack on the Cole has given rise to another, even more disturbing concern--that a large number of high speed boats, each packed with explosives and manned by suicide bombers, could create a "small boat swarm" which could overwhelm the defenses of a warship, particularly in restricted waters where reaction time and maneuverability may be limited. Indeed, recent wargame simulations suggest that such swarm tactics could prove extremely effective against naval battle groups operating in the narrow waters of the Persian Gulf.

Some believed that such "small boat swarm" tactics are best countered with fast, similarly-sized, highly-maneuverable and heavily-armed attack craft which can establish a defensive perimeter at a safe distance from the naval battle group. To this end, appropriately-outfitted Zodiac-type craft have already been deployed for this purpose. However, experience has shown that Zodiac-type craft are only practical in the relatively calm waters of a harbor.

This is because operating Zodiac-type craft at high speed in the turbulent waters of the open sea imposes excessive physical stresses on the crews that can only be withstood for short periods of time. Furthermore, the defensive perimeter should, ideally, be established at a substantial distance from the battle group (e.g., at least 10 miles out), in order to give the battle group sufficient time to react in the event that any of the small boat swarm should penetrate the defensive perimeter established by the Zodiac-type craft. However, due to their light construction, limited operating time at high speeds, and limited fuel-carrying capacity, Zodiac-type craft are not capable of maintaining a reliable defensive perimeter so far out from the battle group. In practice, with Zodiac-type craft, the defensive perimeter must generally be maintained much closer to the battle group, with the consequent loss of reaction time.

It was suggested that attack helicopters might be used to protect a naval battle group when it is at sea or at anchor. However, attack helicopters generally have relatively limited range and, perhaps more importantly, relatively limited sortie time, which effectively prevents them from maintaining a reliable defensive perimeter a substantial distance out from the battle group. Furthermore, attack helicopters generally have substantial radar, infrared and visual "signatures", thereby making them relatively easy to detect and target.

While a number of studies did not discount swarming attacks by larger vessels such as advanced patrol boats, they focused heavily on swarming attacks by very small craft as the predominant scenario that coalition navies operating in littoral waters would have to deal with. The consensus of a number of studies and the opinions of serving naval officers appear to converge and focus on primary threat of massed, small boat threat; that consists of 10 to 20 highspeed manoeuvring boats attacking over a 20-degree to 60-degree azimuth sector. The boats have a simultaneous arrival time with closing speeds of 35 knots. Their manoeuvre is typically in a sinusoidal path. The small boats are considered to be commercial types with no real distinguishing feature to support easy classification. Identification of the attack results from the characteristic behaviour of a large number of high speed, radially inbound boats.

The threat of swarming small boats is not a new one. The US Navy's Operation Prime Chance achieved a stunning success on 21 September 1987. An IRGCN detachment had essentially commandeered an IRIN LST, Iran Ajr, loaded with 18 Sadaf 02 moored contact mines to mine the main channel leading to Bahrain. The frigate USS Jarret (FFG-33) was ordered to investigate the suspicious activity, and two U.S. Army attack helo’s from Jarret caught Itan Ajr in the act of laying mines. Cleared to engage, the Army helos fired rockets and numerous machine gun rounds into the LST, seriously damaging the ship, killing several crew members and causing others to jump over the side.

Not sufficiently chastised (a lesson for any future engagement with Iran), the IRGCN planned to retaliate by attacking targets on the Saudi coast (including potentially the U.S. barges) with a massed attack by about 60 small speedboats (Operation Hajj). Through a good source, U.S. naval intelligence learned of this operation and advance warning was provided to both the United States and the Saudis. However, on the night of the planned attack, 3 October 1987, sea conditions on the Iranian side of the Gulf turned the Iranians’ attempt to form up into a total fiasco and the mission was scrubbed. The Saudi’s reacted with significant naval and air force, but upon finding nothing, accused the United States of crying “wolf.”

Still not giving up, the IRGCN mounted another operation in the night of 8 October, this time with much less intelligence warning. U.S. Army helos from the USS Klakring sighted a group of three Iranian speed boats (one Boghammer and two others) southwest of Farsi Island. One of the Iranian boats fired what was proved to be a U.S.-made Stinger hand-held surface-to-air missile at the helos, which missed. The helos then engaged the Iranian boats, sinking one and heavily damaging two (one of which later sank). The United States rescued six Iranians, but two died from their wounds, and seven Iranians were killed.

The U.S. military in 2002 conducted a war game that simulated large numbers of small and fast Iranian vessels attacking American ships in the Gulf with machineguns and rockets. In the simulation, the U.S. Navy lost 16 warships, to include an aircraft carrier, cruisers, and amphibious vessels in battles that lasted 5 to 10 minutes. The lessons from this game did not gain much intellectual traction in a Pentagon and combatant command fully engaged in today's wars in Iraq and Afghanistan and against al Qaeda.

For a number of years, work in Naval laboratories focused on the small, fast, manoeuvrable boats as the primary threat elements. These reports indicated that forces must be capable of engaging small coastal naval combatants such as patrol boats and guided missile corvettes or other smaller boats. Reports noted that boats could be operated in an unpredictable manner and under unexpected conditions. These reports concluded that these craft may appear as part of the normal friendly or neutral traffic in the area, which makes them all the more difficult to counter. Industry reports provides numerous examples of observed and reported naval exercises by rogue nations that demonstrate their willingness and ability to surreptitiously get inside the effective maximum range of a larger naval force’s surface weapon systems.

The nature and the magnitude of this threat has riveted the attention of some coalition navies who recognised, in general, that a co-ordinated response from networked coalition naval assets is the optimal way to defeat this threat. In an article in the US Naval Institute Proceedings, the incoming US Chief of Naval Operations opined: “Small, fast enemy surface combatants represent another threat to operations in geographically confined areas, where their size and the surrounding clutter of geography and traffic make long-range detection difficult … A diverse force, networked with distributed sensors, offers promising response capabilities once enemy vessels are under way” [Vice Admiral Mike Bucchi and Vice Admiral Mike Mullen, “Sea Shield: Projecting Global Defensive Assurance,” US Naval Institute Proceedings, November 2002, pp 56-59.]

While this swarming small boat attack threat has been discussed in professional journals and discussed in depth in various studies, by 2005 there had been little quantitative analysis to determine the extent to which networking coalition naval platforms can begin to deal with such a threat. Further, at that time there was no extant, standing, international team of likely coalition partners that has begun to analyse this threat, identify potential solutions, and quantitatively define the benefits that would accrue in various scenarios when coalition naval ships, operating in a robustly-networked environment, take on this threat.

In 2005 the UK's Defence Science and Technology Laboratory released a report that categorised FIACs into three subtypes: Type 1 were jet-ski or Boston Whaler craft carrying rocket-propelled grenades (RPGs) credited with a firing range of between 300 m and 500 m; Type 2 were Boghammar or similar fast craft, fitted with unguided multiple launch bombardment rockets, or a larger anti-tank guided weapon with a launch range of a few kilometres; and Type 3 were in effect small fast attack craft (FACs) with small anti-ship missiles or torpedoes, some organic sensors, a degree of command and control, and an endurance of several days.

Type 1	10-50 x boats	Jetski or Boston Whaler with Rocket Propelled Grenade (RPG) weapons or a large blast bomb used in a suicide attack. Credited with a firing range of 3-500m.
Type 2	5-10 x boats	Larger ‘Boghammer’ class boat with an unguided multiple launch bombardment rocket, or a larger anti-tank guided weapon, with launch ranges of up to 8km. The craft has weather protection and accommodation. The small crew allow it to remain at sea overnight.
Type 3	1-5 x boats	Small Fast Patrol Boat (FPB) typified by Super Dvora, with smaller anti-ship missile or torpedo armament, and degree of sensor and Command and Control (C2) fit. Weapon ranges of 4 km (torpedo) out to 15 km (ASM) The vessel has more endurance than Type 2, allowing mission duration’s of several days.

Iran is one of the few countries to employ artillery rockets as an offensive anti-ship weapon. The tactic was first used out of economy in the Iran-Iraq war, possibly influenced by similar equipment of the North Korean Navy. Such MLRS mounted on small craft are generally inaccurate and lack the single-hit firepower of anti-ship missiles or torpedoes, but can seriously damage unarmed civilian traffic and certainly deter ships from sailing. In some situations they could set the ship on fire or disable key machinery, but are unlikely to actually sink a large civilian ship such as an oil tanker. Although some exercises suggest the use of a flotilla of MLRS craft in a single attack, a typical engagement model would likely be a few such craft approaching the transiting tanker and firing their rockets from about 500m away, slowing to about 1.5 times the target’s speed and weaving to allow alternate craft to fire while the others reload. Most MLRS craft use the 107mm Haseb rocket (Chinese 'Type-63') but some, such as the C-14 class carry the larger BM-21 122mm system. Early MRLS craft had the rockets mounted such that they could only be fired to the sides, but more recent designs nearly always position them on the cabin roof firing forwards.

The American escorts’ medium calibre gun (a US 5”/54 or the UK 4.5” Mk 8) will typically fire 20-25 rounds per minute out to about 25km, with either direct action (DA) fusing (exploding on impact with the sea or a target), or via a Variable Time (VT) proximity fuse for airburst over the target, which is attacked by the shell fragments. These medium calibre guns cannot generally be used against single FIAC targets, due to shortcomings in the ships detection and ID sensors, which are optimised against larger targets.

In 2009, a US Office of Naval Intelligence (ONI) report titled 'Iran's Naval Forces - From Guerrilla Warfare to a Modern Naval Strategy' articulated how the IRCGN seeks to achieve tactical success, noting that "modern small boats are capable of high speed, have very shallow drafts, can be difficult to detect because of their small size, and may not be positively identified even when detected". This leaves them "well suited for conducting hit-and-run style attacks".

FIACs tend to operate in groups, or 'swarms'. "Operating in groups affords small boats better combat capabilities through mutual protection, while also increasing their offensive firepower … so they will typically rely on mass and manoeuvre to overwhelm their target, anticipating that some of the small boats will penetrate a ship's defenses," it stated.

Alex Carter and Damian Fernando wrote "Small boats are hard to detect by most sensors – they lie low in the water. Small boats can take any shape or size. Additionally, the enemy’s decision as to the choosing of the time, place and mode of attack against a naval or commercial platform is made easier by his ability to move a small boat or groups of small boats quickly to an area. Moreover, an innocent looking fishing vessel, a jet ski, a pleasure boat or any other specially designed small fast boat could easily be converted to a lethal suicide boat to carry high explosives to inflict heavy damages. Small boats have the advantage of maneuver in places where vessels have to maneuver at slow speeds, such as maneuvering through channelized shipping lanes or in other areas with traditionally high numbers of vessels. ... small boats are a perfect and deadly tool of choice to employ devastating swarming tactics to achieve desired violent effects on the sea. Small boats disguised as typical fishermen in certain traffic congested areas can easily target merchant ships."

Milan Vego wrote "The Iranian concept employs a large number of small boats to surprise and isolate a force of the enemy’s large surface ships. The boats converge to their prospective targets from a large number of bases and attack using ambushing positions close to the Iranian coast or offshore islands. The greatest potential problem here is with small craft in the 21-mile-wide Strait of Hormuz. On Jan. 7, five Iranian boats approached a three-ship U.S. formation (the cruiser Port Royal, the destroyer Hopper and the frigate Ingraham), maneuvering aggressively. Three of these boats approached within about 300 yards of the U.S. ships. This incident lasted about 20 minutes and no physical contact occurred. The U.S. ships conducted some evasive maneuvers and were ready to take appropriate action before the Iranian boats suddenly broke away. "Such swarming attacks were predicted by retired Marine Lt. Gen. Paul van Riper, who played the commander of the red enemy side during the Millennium Challenge exercise in July and August 2002. He creatively used swarming tactics that resulted in the sinking of an aircraft carrier and 16 other ships. The red small boats attacked with machine guns and rockets, reinforced with air- and ground-launched missiles. Some of the small boats were loaded with explosives to detonate alongside U.S. ships in suicide attacks."