How the U.S. Navy can defeat Iran’s swarm attacks?

Iran Swarm Attack
Iran Swarm Tactics

On May 10, 2021, a group of 13 Iranian Islamic Revolutionary Guard Corps Navy (IRGCN) fast in-shore attack craft (FIAC), a type of speedboat armed with machine guns, conducted unsafe and unprofessional maneuvers near U.S. naval vessels transiting the Strait of Hormuz. 

This incident was not the first one. Similar incidents have occurred regularly for decades and have come to represent Iran’s primary method of provocation in the Persian Gulf and beyond.

United States Naval forces conducting straits transits face a host of unique force protection challenges. Traffic density is often high, with many ferries, fishing and pleasure boats, and large cargo ships maneuvering in a small area. Although the Rules of Engagement (ROE) will generally designate query and warning ranges, international law and freedom of navigation allow vessels to operate in very close proximity to warships. Small vessels are often difficult to regulate, and many lack basic equipment such as the bridge to bridge radios. With a host of stationary and seemingly randomly moving boats, determining a hostile action in a timely manner is difficult at best. These conditions make the identification of and defense against hostile small craft extremely difficult. Even after a craft is designated hostile, the timeline for mounting an effective defense is often noticeably short.

irgc boats
IRGC Boats

The proliferation of longer-range mobile guns, including the possible emergence of lasers, electronic warfare or boat-launched drone attacks, all make the prospect of facing swarms of armed, fast-moving small boats even more dangerous for surface ships. Furthermore, some small manned boats carry and fire portable land weapons such as RPGs, Anti-Tank Guided Missiles, or various medium-caliber portable guns aimed at ship structures.

The number one enemy to a Commander attempting to protect his ship against small boat attack is time. It is central to the problem because many factors compress reaction times in these situations. Among these factors are physical speed, geographic separation, identification, and maneuverability. Current doctrine for strait transits generally dictates that the faster a strait transit can be accomplished the better. Unfortunately, when dealing with small craft, this may equate to closure rates more than 50kts or 84.47 Feet per Second. Assuming that an unmarked vessel loitered in traffic until it was 500 feet from a U.S. warship before accelerating towards the ship at max speed the small boat would reach the ship in 5.91 seconds.

irgc naval exercise 2015
IRGC Naval Exercise 2015

One small boat can pose a threat to a destroyer, however it can be neutralized even with the problems stated above. But the problem is bigger. There could be a lot of boats approaching at the same time for a swarm attack. Swarm attacks are high-risk, coordinated assaults sometimes directed against multiple targets. They are extremely difficult to defend for many reasons, one of them simply being numbers and redundancy; if there are so many spread out, yet fast-approaching small boats, it could be difficult for deck-mounted ship guns or overhead assets such as drones or helicopters to destroy enough approaching targets at one time. The saturation of sensors and weapons, radar tracking problems, limited time for kill assessment, automatic sensor weapon allocation problems make it almost impossible to counter all of the targets.

When compared with the US, Iran has the limited military capability. Iran is trying to fill this gap with swarm tactics. Instead of matching the U.S. military weapon-for-weapon, Iran deploys large numbers of relatively unsophisticated systems at sea. Iran’s Revolutionary Guard has long worked on swarming tactics for small boats against large naval vessels. 

How a warship can defeat swarm attacks

For an effective defense against swarm attacks, there should be a layered defense approach. This layered defense should contain unmanned systems (including UAV, USV, and loitering munitions), air assets, guided missiles, laser weapons, and crew-served weapons. 

To counter small boat threats, the U.S. Navy has developed a Surface Warfare Mission Package (SUW), an integrated weapons system for Littoral Combat Ships. SUW is engineered to destroy small craft approaching at speeds up to 35 knots or more. The weapons are intended to reinforce one another and operate in a synchronized fashion. The SUW’s Missile Module comprises 24 ship-fired Longbow Hellfire Missiles, 30-and-57mm guns, 11-meter rigid hull inflatable boats, helicopters, and vertical-take-off-and-landing ship-launched drones. 

The ship launched Hellfires, for instance, can utilize all-weather millimeter-wave radar, inertial guidance, or semi-active laser targeting to fire upon enemy ships, helicopters, fixed-wing assets, or drones attacking the LCS. The concept with the overall module is to enable each platform to function as a “node” on a larger network.

The U.S. Navy is also testing and developing a “ghost fleet” of small unmanned ships to perform a range of missions to include, reconnaissance, mine and submarine detection and of course forward-operating attack missions – firing weapons while manned crews remain at safer distances.

Crew Served Weapons 

The standard weapons employed for self-defense on DDGs are the 7.62mm M-60, the Browning .50 caliber machine gun, and the Mark 38 – 25 mm machine gun system. A recent addition to the fleet is the dual .50 cal mount allowing a single gunner to operate two weapons simultaneously.

mk 38 gun is fired on uss arleigh burke ddg 51 in july 2014 - naval post- naval news and information
The guided-missile destroyer USS Arleigh Burke (DDG 51) fires its MK 38 25mm machine gun during a live-fire exercise. (U.S. Navy photo)

The standard configuration for an Arleigh Burke DDG is 2x 25mm chain guns on the port and starboard amidships, 2x M-60s on the port and starboard bridge wings, and up to 8 .50 caliber weapons arrayed from fore to aft. B 

The .50 cal, while an excellent weapon in its own right, is over 50 years old. The addition of the dual .50 cal mounts to the fleet is a step in the right direction, but it alone is insufficient.

Armed Surveillance Drones/Helicopters

Forward-operating armed surveillance drones, for instance, can send real-time images to helicopters and ship-based fire control radar, enabling faster response time. Armed helicopters can more quickly find and attack targets, if they are identified and transmitted from other assets such as drones or ship-based sensors. Not only could the boats perform sensing and reconnaissance missions, but they could of course also themselves become explosives or seek to jam a ship’s radar by flooding it with dispersed attack nodes.

us navy unmanned aerial vehicle mq 9b sea guardian operates with naval assets - naval post- naval news and information
US Navy Unmanned Aerial Vehicle MQ-9B Sea Guardian Operates with Naval Assets


​Small, fast-transport 11-meter inflatable boats can also function in a key defensive capacity against small boat attacks. Often used as rapid entry or small attack vehicles for Navy SEALs and other Special Operations Forces, 11-meter inflatable boats can provide ship crews with an ability to leave the ship and “engage” approaching small-boat attackers, providing yet another element of defense.

australia rib on mission - naval post- naval news and information
RHIB on mission

Air Force Assets

In the past, U.S. Navy conducted some exercises with U.S. Air Force assets to practice its defense capabilities against swarm attacks. AC-130W Stinger II, A-10 Warthog, and F-15E Strike Eagles were used as a weapon platform for engaging boat swarms during these exercises.

a10 wartdog - naval post- naval news and information
An A-10 Thunderbolt IIs with the 74th Fighter Squadron from Moody Air Force Base in Georgia flying over the Gulf of Mexico on February 7 during a weapons-system evaluation program at Eglin Air Force Base in Florida. (US Air Force Photo)

Loitering Munitions

When employed from a ship, the loitering munitions can engage targets at sea or on land. In a sea domain, these munitions could collect intelligence, assess targets, and strike. These systems could be integrated into ships’ combat management systems and used with the other onboard systems. These drones can help counter swarm boat attacks.  

A recent contract to Raytheon shows that the U.S. Navy plans to use these loitering munitions on USVs and UUVs. It will add a new dimension to naval warfare. Ships could face tens of drones launched from a UUV anywhere in the naval theater. 

iai harop system (image: iai)
IAI HAROP System (Image: IAI)

Unmanned Surface Vessels

In the future shipborne armed unmanned surface vessels will be used for one of the first-line defense asset. Ships will use their organic USVs for escort mission.

Turkish ULAQ USV (Photo courtesy of Anadolu Agency)

Laser Weapons

The U.S. Navy installed the first Optical Dazzling Interdictor, Navy (ODIN), a laser weapon system that allows a ship to counter unmanned aerial systems. ODIN is one of many laser-directed energy weapons the Navy has in development now as part of its larger Navy Laser Family of Systems (NLFoS) effort. ODIN features a relatively low-powered laser designed to work as a dazzler to blind electro-optical and infrared optics. This could be used to confuse optical or imaging infrared seekers on incoming weapons, such as anti-ship cruise missiles, throwing them off course. It could also neutralize cameras used for intelligence, surveillance, and reconnaissance (ISR) purposes on other ships, manned aircraft, and drones. ODIN is just one of the new laser-directed energy weapons the U.S. Navy has in the works now. 

uss portland
USS Portland

On May 16, 2020, the U.S. Navy announced that Amphibious transport dock ship USS Portland (LPD 27) successfully disabled an unmanned aerial vehicle (UAV) with a Solid State Laser – Technology Maturation Laser Weapon System Demonstrator (LWSD) MK 2 MOD 0. Mk 2 Mod 0 Laser Weapon System Demonstrator (LWSD), a much more powerful 150-kilowatt class design which is intended to use against UAVs and small crafts. 

It is likely that in the near future, these weapons will be used against swarm attacks. 


These small boats will become big trouble for ships in near future. It is not only Iran; many countries are working on unmanned surface vehicles to use them for swarm attacks. The biggest challenge for the U.S. appears to come from China, which is developing the swarming capability to neutralize the U.S. advantage in aircraft carriers. Navies must be prepared for this threat very well and develop new advanced AI-powered equipment against it.

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