Deck-Mounted Guns, Missiles & Air Power: How U.S. Navy Ships Can Counter Small Boat Swarms

By Kris Osborn, Warrior

The pace at which Iran is losing surface ships and mines seems faster than the world can follow, yet Iran still poses a significant military threat in the Strait of Hormuz for several key reasons. Of course “sea mines” remain a substantial threat, despite advanced U.S. Navy mine-hunting technology, yet they can still be found by undersea drones and mine-clearing surface ships. 

U.S. Central Command recently released video of successful U.S. strikes on Iranian mine-laying vessels in waters in or near the Strait of Hormuz, yet the mine-threat likely remains quite pressing as the U.S. Navy considers its combat options. 

Large Warships Vulnerable? 

Drone swarms and small boat swarms are also certain to present a serious threat to both commercial and military traffic transiting the Strait of Hormuz. In large measure, the reason pertains to proximity, meaning the short distances between the Iranian coastline and the waterways of the Strait of Hormuz. The Strait of Hormuz is only 35-to-60 miles wide, a condensed area quite vulnerable to drone and small boat attacks. 

Both drones and small boats attack with a similar operational concept, as they are designed to simply “overwhelm” ship defenses by blanketing a target area from multiple angles and points of attack at one time.  Large groups of swarming small boats, for example, is something Iran has used for many years to harass or intimidate military and commercial vessels crossing the Strait of Hormuz. While small boats armed with guns might quickly be destroyed by deck-mounted guns on Navy ships, the challenge simply becomes one of “volume” and “area.” Large numbers of small boats, potentially filled with explosives, could attack a large surface ship at one time to create more targets and more angles of approach than deck mounted guns could successfully track, target or destroy.  The Iranians could potentially fill large numbers of drone-boats with explosives and launch them at large surface warships ill-equipped to stop large numbers of them at one time. 

Countering Small Boats

Is there a viable defense against small boat swarms?  U.S. Navy drones, helicopters and surveillance planes could create a substantial measure of difference; groups of small boats would need to be “seen” and “destroyed” from the air before coming within striking range of large surface warships. U.S. Navy MH-60R helicopters and ship-launched drones could conduct reconnaissance missions through a large area to generate a protective envelope in which approaching small boats could potentially be neutralized by air-to-surface weapons such as guns, missiles and rockets. Hellfire missiles or Hydra-70 laser guided rockets could be used to destroy small boats from the air, and helicopter mounted weapons such as a Gatling Gun or .50-cal machine gun could even blanked small boat groups with suppressive fire. 

Drone Swarm Threat

Swarms of aerial attack drones could only further compound the risks to U.S. warships in the area given that they too could operate with a proximity advantage, given how “narrow” the Strait of Hormuz is. Unlike U.S. Navy warships in the Red Sea, which operated with stand-off distance from shore, ship-integrated AEGIS radar and a multi-domain ability to intercept or counter attacking drones with aircraft, deck-mounted guns or ship-fired interceptors, U.S. Navy ships in the Strait of Hormuz operate with a much smaller geographical or range “window” through which to “see” and “counter” incoming swarms.  The U.S. Navy had great success countering Houthi-fired cruise missiles, drones and rockets in the Red Sea, yet a close-in small boat or drone swarm attack in the Strait of Hormuz presents a more complex and altogether different threat equation.  Countering drone “swarms” in the Strait of Hormuz from surface ships would similarly present a complex threat, as swarms may simply present too many approaching targets for deck-mounted guns, ship-fired interceptors or other kinds of ship defenses such as SeaRAM rockets or the Close-in-Weapons-System. Even though the rapid arrival of “proximity fuses” able to disperse fragments through an “area” to destroy multiple drones at one time could prove effective, ultimately a non-kinetic countermeasure such as EW or High-Powered Microwave might prove more effective against a swarm. 

U.S. Navy Ship Defenses 

Over the years, Iranian small boats have taken off quickly when US warships arrive? The answer may seem simple and self-evident given the firepower of Navy destroyers. However, small boats have shown an ability to present a significant military threat to large warships, a reason why the US Navy has in recent years taken specific and impactful measures to improve ship-defences. The service has conducted numerous live-fire drills and scenario reenactments to sharpen its ability to counter and destroy swarming small boat attacks. For example, most surface Navy warships operate with a ship-defense weapon referred to as Close-In-Weapons-System, or CWIS, a phalanx gun “area” weapon able to fire hundreds of small metal projectiles across a wide envelope in seconds to destroy incoming enemy missiles, aerial drone swarms and even lower flying helicopters or other fast-incoming attacks. However, roughly 10 years ago the Navy upgraded CWIS into what’s called a “1b” variant expanding its aperture from purely air-defense to counter-surface. The new 1B variant, which is now operational across Navy warships, specifically enables the fast-firing Phalanx area weapon to “blanket” incoming small boats across a wide “surface” area, essentially denying any ability for small boats to survive moving close in to large warships. A surface-firing CWIS, therefore, might be well positioned to stop, disable or simply destroy a large number of swarming small boats in a way other weapons could not.

Also, small short-and-mid range deck fired interceptors such as SeaRAM and Rolling Airframe Missile have been massively upgraded to increase range, lethality and precision, weapons enhancements increasingly capable of targeting and destroying fast-moving small boats. These weapons upgrades go back as far as 2015 when the Navy’s surface force implemented a fleet-wide “distributed lethality” program to massively arm the surface fleet with a new generation of more capable weaponry. The concept was to help the Navy transition from what was primarily a counter-terrorism role during the Iraq and Afghanistan wars into a “blue-water” and “open water” fighting force capable of destroying large, high-tech, great power warships.

US Navy Maritime Air Power 

Finally, yet another critical factor is, quite simply, the air assets the Navy can deploy from amphibs and destroyers. Amphibious assault ships, such as the USS Bataan now in the region, can carry more than 24 rotary-wing and fixed wing attack aircraft, including the F-35B and MV-22 Osprey. Therefore, should US amphibs dispatch armed F-35Bs over the waters in the region, Iranian small boats would likely instantly be aware of their vulnerability. With its long-range, precision sensors and next-generation air-to-surface weaponry, a single F-35B would be positioned to obliterate groups of swarming small boats. Sensors on an F-35B, especially if networked with US Navy drones and other air and surface assets, could see and track Iranian small boats from substantial stand-off distances. 

Kris Osborn is the President of Warrior Maven – Center for Military Modernization. Osborn previously served at the Pentagon as a highly qualified expert in the Office of the Assistant Secretary of the Army—Acquisition, Logistics & Technology. Osborn has also worked as an anchor and on-air military specialist at national TV networks. He has appeared as a guest military expert on Fox News, MSNBC, The Military Channel, and The History Channel. He also has a Masters Degree in Comparative Literature from Columbia University