The Red Sea Shipping Crisis: A Window into the Strengths and Vulnerabilities of Today’s Naval Defense

Since mid-November 2023, the Yemeni insurgent group Ansar Allah (Partisans of God), commonly known as the Houthis, has launched hundreds of attacks on merchant ships in and around the Red Sea, endangering the principles of freedom of navigation and the unabated flow of seaborne commerce.[1] To counter a complex mix of conventional and hybrid threats emanating from Houthi-controlled territories in Yemen and restore the safety of international shipping lanes, Western nations have established naval coalitions and deployed a significant number of naval assets in the region.[2] The armed engagements between the Houthis and Western surface combatants shed some light on the strengths and vulnerabilities of today’s naval defense.

Combat-proven Tag

The successful combat debut of several ship-based air defense solutions is a testament to the strides made by Western nations in developing reliable, high-end performance anti-air warfare (AAW) systems.

On March 21, 2024, a French FREMM frigate, operating in the southern Red Sea as part of the European Union’s Operation Aspides, downed three Houthi ballistic missiles.[3] The French Navy has not disclosed the kind of munition used. Still, naval experts are convinced that Aster 30 long-range surface-to-air missiles were most likely involved in the shoot-down, representing the Aster 30 missile’s first operational use in combat.[4] The European consortium MBDA produces the Aster missile family, including the Aster 15 short-to-medium-range missile. High G maneuverability (g-force maneuvers involve high acceleration levels), short preparation-to-engagement time, and high-performance active radar homing combine to make the Aster missiles an all-round anti-air defense solution with unrivaled hit-to-kill capability.[5]

On April 9, 2024, an Israeli Navy’s Sa’ar 6 corvette successfully used the Rafael-made C-DOME air-defense system to shoot down a hostile aerial projectile in southern Israel, scoring the first-ever combat kill for the Iron Dome system interceptor’s naval version.[6] The C-DOME is a ship-mounted modular configuration that provides 360° coverage for ship shelf-defense and area defense against multiple air threats, including cruise missiles, artillery projectiles, and unmanned aerial vehicles (UAVs).[7] It has become standard practice for the Israeli Navy to bolster its Sa’ar 6 corvettes’ air defense array by integrating two C-DOME systems on board, which complement the warship’s 32 vertical launch cells (VLCs) for Barak-8 surface-to-air missiles with 40 Tamir interceptor missiles.[8]

Amid Iran’s large-scale air attack against Israel on April 14, 2024, two U.S. Navy Arleigh Burke-class missile destroyers – the USS Arleigh Burke and USS Carney – successfully downed Iranian ballistic missiles with RIM-161 Standard Missile-3 (SM-3) interceptors, marking the first combat kill of SM-3s. The two destroyers were fitted with state-of-the-art solutions in the U.S. anti-ballistic arsenal: the Aegis Ballistic Missile Defense (BMD) system and the SPY-1D radar.[9] The SM-3 is an exo-atmospheric missile defense interceptor designed to neutralize short- to intermediate-range ballistic missiles during their midcourse phase with a kinetic warhead.[10] In other words, the SM-3 intercepts an enemy target roughly at the apex of its ascendant flight path outside the Earth’s atmosphere and destroys it upon impact through hit-to-kill technology. The U.S. Navy has successfully tested the SM-3s dozens of times in controlled environments. Still, the fact that its BMD-capable warships are now combat-proven further strengthens trust in the weapons system.

In addition to the success of missile solutions, some other ship-integrated defensive systems have also had the chance to prove their tactical value and reliability under high-intensity combat conditions. These defense solutions include gun armaments, embarked rotary-winged aircraft, and jamming systems.

On January 30, 2024, the U.S. Navy Arleigh Burke-class missile destroyer USS Gravely deployed its MK 15 Phalanx close-in weapon systems (CIWS) to destroy a Houthi anti-ship cruise missile within one nautical mile of the surface combatant, marking the first combat kill of a CWIS since the beginning of the Houthi anti-shipping campaign.[11]

The Phalanx CIWS is an automated machine gun for close-range intercepts that uses rapid-fire – up to 4,500 rounds per minute – to suppress inbound threats.[12] It represents the latest line of a warship’s multi-layered defense architecture, which activates when a hostile target penetrates the outer defenses.

While patrolling the Red Sea, on March 2, 2024, the Italian Navy Andrea Doria-class destroyer Caio Duilio neutralized a Houthi UAV about 6km from the warship.[13] The OTO Melara 76/62 Super Rapid Gun Mount – its rapid-fire naval gun – shot down the drone.[14] Although primarily designed for anti-aircraft, anti-surface, and ground-support roles, the 76mm can perform short-range anti-missile/anti-drone point defense functions when serviced with DART-guided projectiles.[15] Already exported to dozens of countries in Europe, Asia, and the Middle East, this drone shoot-down further strengthens the 76mm’s iron-clad reputation as a top-notch naval gun.

On March 20, 2024, a French Navy helicopter knocked down a Houthi UAV with machine-gun fire bursts, scoring the first combat debut for a door-mounted machine gun in an anti-drone role in the Red Sea offensive’s context.[16] Either a Eurocopter AS565 Panther or an NHIndustries NH90 – rotary-wing aircraft generally embarked on by the French Navy’s principal combatants – was used in the encounter. Typically, two multi-purpose military helicopters carry high-caliber main guns, missiles, and up to two 7.62mm door guns. The successful rotary-wing-on-drone action proved that light-caliber machine guns represent a combat-proven, cost-effective tactic to neutralize slow-flying threats.

In October 2024, a French FREMM frigate deployed two counter-unmanned aerial systems (C-UAS) – the Neptune and the MAJES DB6 – to neutralize a Houthi UAV in the Red Sea. These anti-drone jamming systems had been hastily installed into the French Navy's first-rank surface combatants after showcasing promising results during the counter-drone Wildlife exercise in September 2024.[17]

The swift fitting of C-UAS systems is not an isolated episode but rather the most recent manifestation of a broader shift in the French Navy’s strategy to bolster fleet preparedness against emerging aerial and naval threats.[18] These measures included accelerating the deployment in operation of brand-new technologies and fast-tracking the installation of solutions based on the return of experience (RETREX) by military personnel deployed in the Red Sea, as happened in March 2024 with the decision to fit the Paseo XLR advanced electro-optic infra-red (EO/IR) system on all the French Navy’s principal warships.[19]

The French Navy has also sought to bolster its counter-drone readiness through intensive training. Since mid-2023, it has regularly conducted anti-drone naval drills to neutralize hostile UAV/USV threats through a mix of deck-mounted automated gun armament, heavy machine guns, and shotguns loaded with anti-light drone ammunition (ALDA) rounds.[20]

Table 1. Main missiles in use with U.S., European, and Israeli surface combatants

Source: Data elaborated by the author.

Cumbersome Constraints

Despite several successful military measures to counter the Houthis, the Red Sea crisis has also laid bare three main vulnerabilities hindering the capabilities and readiness of Western naval forces: namely, missile magazine capacity, system failure, and friendly fire.

Missile Magazine Capacity

The lack of rapid at-sea rearming capabilities has emerged as the most concerning limitation of ship-based air defense. When operating in saturated air defense environments, a surface combatant is likely to deplete the magazine capacity of its VLS canisters at a quicker pace. The standard shot doctrine of most navies when engaging incoming aerial threats is to fire more than one interceptor to maximize the neutralization’s chances. Therefore, the faster a warship’s stockpiles of missiles on board narrow due to enemy attacks, the weaker its capacity to conduct sustained independent operations in contested waters will be.

The impossibility of conducting at-sea reloading of VLS canisters bears two significant shortcomings. First, it forces a warship to shorten its planned deployment. Second, as a surface combatant leaves the conflict theatre to reach a safe port for replenishment, its absence from the station creates security gaps in the operational area.

Table 2. Anti-air warfare capabilities of principal U.S., European, and Israeli warships

Source: Data elaborated by the author.

Cognizant of the underlying risks of limited magazine capacity and determined to strengthen the operational flexibility of surface combatants, Western navies are exploring concrete measures to close this capability gap. To this end, the U.S. Navy conducted a transfer of an empty VLS canister between the support ship USNS Washington Chambers and the Ticonderoga-class cruiser USS Chosin off the coast of San Diego, California, in mid-October 2024. During the test, all eyes were focused on the Transferable Reload At-sea Method (TRAM) system, an expeditionary reloading equipment developed by the U.S. Navy’s Naval Surface Warfare Center, Port Hueneme Division in California.[21] To be installed on auxiliary ships, the TRAM consists of a crane system capable of lifting and rotating a missile canister vertically before depositing it into a launcher cell.[22] Commenting on the at-sea reloading test, the U.S. Secretary of the Navy, Carlos Del Toro, described the TRAM as a “game-changing”[23] technology that strengthens the U.S. Navy’s capacity to conduct sustained operations in forward areas under high-intensity conditions.

Similarly to its Atlantic ally, the French Navy has also made strides in testing at-sea resupply and reload VLS capabilities. In May 2024, the replenishment ship Jacques Chevallier and the aircraft carrier Charles de Gaulle conducted transfer and siloing operations of an Aster missile while underway at sea. A truck-mounted crane on the aircraft carrier’s flying deck was used to position the missile into the VLS cell.[24] A month later, the Jacques Chevallier conducted a restock test with the Aquitaine-class frigate Lorraine. This time, the auxiliary ship’s crane was involved in the siloing operation of a VLS missile canister.[25]

However, although these tests showcase groundbreaking progress in at-sea replenishment capabilities, restocking missile payloads in open waters is far from a one-size-fits-all solution.[26] Taking the TRAM system as an example, three main factors hinder its short- and medium-term deployment. First, despite the promising results showcased during ashore and offshore tests, the TRAM is still at the prototype stage. According to U.S. Navy Secretary Del Toro, fielding it will take two to three years. Second, under its current guise, TRAM is designed to conduct replenishment operations in moderate weather conditions up to sea state 5 (wind’s intensity between 17 and 21 knots and waves as high as six or eight feet). Finally, deploying at-sea VLS reload-capable auxiliary ships raises the imperative of ensuring their security through escort warships.

System failure

Layered self-defense systems are critical to the survival of ships and the safety of the crewmembers in case of system failure. Two engagements between the Houthis and Western coalition forces have underscored how having self-defense redundancies makes the difference between life and death in combat zones.

First, the Dutch Iver Huitfeldt-class frigate Niels Juel suffered a weapon systems malfunction when engaging a Houthi UAV swarm in March 2024. While the warship shot down the hostile targets, the system failure prompted the Dutch Navy to the Niels Juel’s immediate withdrawal from the station.[27] Second, deploying the Phalanx CIWS by the USS Gravely to neutralize an enemy cruise missile is far from ideal and speaks volumes about a potential breach in the destroyer’s outer defenses. Indeed, using missile systems and large-caliber naval guns rather than CIWS to knock out high-speed threats is standard practice. Although qualified for anti-missile roles, the Phalanx system is not the weapon of choice for countering incoming missiles due to its limited operational range, making it highly effective against comparatively slower-flying hostile targets.

Friendly Fire

Although only two friendly fire accidents occurred in over a year of naval operations, these episodes underscore that the risk of misidentification is high in the fog of war. On February 26, 2024, the German Navy’s Sachsen-class frigate Hessen mistakenly identified a U.S. MQ-9 Reaper UAV as a hostile threat and, after coordinating with coalition allies, fired two SM-2s at it. Fortunately, the frigate’s counter-measures missed the American drone.[28] Undoubtedly, the fact that the MQ-9 Reaper was flying with its Identification, Friend, or Foe (IFF) transponder signal turned off alimented confusion. However, naval experts posit that the German Navy’s dated radar systems bear part of the responsibility for the attempted shoot-down, arguing that state-of-the-art radar systems could have recognized the incoming drone as a friendly UAV through its electromagnetic signature.[29] On December 21, 2024, the Ticonderoga-class guided-missile cruiser USS Gettysburg, which serves as an escort vessel in the USS Harry S. Truman aircraft Carrier Strike Group, shot down a F/A-18 Super Hornet fighter jet part of the Strike Fighter Squadron 11 embarked on the Truman in a friendly fire incident over the Red Sea. The two pilots successfully ejected before impact, reporting only minor injuries.[30] The two incidents speak volumes about the urgency to strengthen command-and-control structures and maritime situational awareness, especially when multiple naval coalitions are deployed in high-intensity operational contexts with consistent risks of multi-domain swarm attacks.

Conclusions

The several first operational interceptions scored by counter-Houthi naval forces have strengthened trust in the combat effectiveness of modern AAW solutions. However, the Red Sea experience is far from being considered a complete success story. When confronting the Houthis, Western coalition allies have also come to grips with worrisome capability gaps and the multipronged challenges of operating in a saturated air defense environment. Taking stock of lessons learned and swiftly integrating effective solutions is paramount for Navies determined to successfully counter a combination of conventional and emerging threats in the aerial and naval domains. This urgency is further accentuated by the fact that the Houthi menace – albeit insidious and lethal – positions between the low and medium ends of the threat spectrum regarding capability. Western naval forces must adopt high-performing solutions to withstand threats by near-peer state opponents in future high-end conflicts. These include intensifying counter-hybrid threat exercises, expanding the use of small-size missiles that could be quad-packed in a single VLS cell (such as the RIM-162 ESSM), and accelerating the deployment of cutting-edge anti-drone and at-sea replenishment technologies.

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References:

[1] Michael Knights, “A Draw Is a Win: The Houthis After One Year of War,” Combatting Terrorism Center at West Point, vol. 17, no. 9, October 2024, https://ctc.westpoint.edu/a-draw-is-a-win-the-houthis-after-one-year-of-war/.

[2] U.S. Department of Defense, “Statement from Secretary of Defense Lloyd J. Austin III on Ensuring Freedom of Navigation in the Red Sea,” 18 December 2023, https://www.defense.gov/News/Releases/Release/Article/3621110/statement-from-secretary-of-defense-lloyd-j-austin-iii-on-ensuring-freedom-of-n/; Leonardo Jacopo Maria Mazzucco, “Operation Aspides: The European Union’s Response to the Red Sea Crisis,” The Arab Gulf States Institute in Washington, 3 April 2024, https://agsiw.org/operation-aspides-the-european-unions-response-to-the-red-sea-crisis/.

[3] Harry Papachristou, “French frigate repels Houthi missile salvo targeting boxship in Red Sea (Video),” Trade Winds, 21 March 2024, https://www.tradewindsnews.com/casualties/french-frigate-repels-houthi-missile-salvo-targeting-boxship-in-red-sea-video-/2-1-1616333.

[4] Xavier Vavasseur, “French Navy Air Defense FREMM Intercepts 3 Ballistic Missiles,” Naval News, 21 March 2024, https://www.navalnews.com/naval-news/2024/03/french-navy-air-defense-fremm-intercepts-3-ballistic-missiles/.

[5] MBDA, “ASTER 15 & 30,” https://www.mbda-systems.com/product/aster-15-30/.

[6] Rafael, “C-DOME FIRST COMBAT INTERCEPTION,” 11 April 2024, https://www.rafael.co.il/news/idf-announces-rafaels-c-dome-first-combat-interception-of-hostile-target-at-sea/.

[7] Rafael, “C-DOME,” https://www.rafael.co.il/system/c-dome-2/?utm_source=google&utm_medium=CPC&utm_term=C-Dome_gsn&gad_source=1.

[8] Thomas Newdick, “Israel’s Ship-Based Iron Dome Just Got Its First Combat Kill,” The War Zone, 9 April 2024, https://www.twz.com/land/israels-ship-based-iron-dome-just-got-its-first-combat-kill.

[9] Sam LaGrone, “SM-3 Ballistic Missile Interceptor Used for First Time in Combat, Officials Confirm,” USNI News, 15 April 2024, https://news.usni.org/2024/04/15/sm-3-ballistic-missile-interceptor-used-for-first-time-in-combat-officials-confirm.

[10] Missile Threat – CSIS Missile Defense Project, “Standard Missile-3 (SM-3),” March 9, 2023, https://missilethreat.csis.org/defsys/sm-3/.

[11] Geoff Ziezulewicz, “A Houthi missile got within a nautical mile of USS Gravely on Tuesday,” Navy Times, 1 February 2024,

https://www.navytimes.com/news/your-navy/2024/02/01/a-houthi-missile-got-within-a-nautical-mile-of-uss-gravely-on-tuesday/.

[12] General Dynamics, “NAVAL PLATFORM SYSTEMS Phalanx CIWS,” https://www.gd-ots.com/armaments/naval-platforms-system/phalanx/.

[13] Ministero della Difesa, “Difesa: nave Duilio abbatte drone nel Mar Rosso,” 2 March 2024, https://www.difesa.it/primopiano/difesa-nave-duilio-abbatte-drone-nel-mar-rosso/48363.html.

[14] Thomas Newdick, “Italian Destroyer Guns Down Houthi Drone With 76mm ‘Super Rapid’ Cannon,” The War Zone, 4 March 2024, https://www.twz.com/sea/italian-destroyer-guns-down-houthi-drone-with-76mm-super-rapid-cannon.

[15] Leonardo, “OTO 76/62 SR SUPER RAPID GUN MOUNT,” https://electronics.leonardo.com/documents/16277707/18404219/Cannone+OTO+76_62+SR.pdf?t=1671011143614.

[16] Xavier Vavasseur, “French Navy Helicopter Shoots Down Houthi drone in Red Sea,” Naval News, 20 March 2024, https://www.navalnews.com/naval-news/2024/03/french-navy-helicopter-shoots-down-houthi-drone-in-red-sea/.

[17] Martin Manaranche, “ French Navy counters UAV for the first time thanks to jamming solution,” Naval News, 6 December 2024, https://www.navalnews.com/naval-news/2024/12/french-navy-counters-uav-for-the-first-time-thanks-to-jamming-solution/.

[18] Institute for Higher National Defence Studies, “Admiral Vaujour: "The Navy must be resilient and retain operational superiority",” https://ihedn.fr/en/lundis-de-lihedn/amiral-vaujour-la-marine-doit-etre-resiliente-et-conserver-la-superiorite-operationnelle/.

[19] Xavier Vavasseur, “France is Fitting Paseo XLR EO/IR System on all its FREMM and Air Defense Destroyers,” Naval News, 12 March 2024, https://www.navalnews.com/naval-news/2024/03/france-is-fitting-paseo-xlr-eo-ir-system-on-all-its-fremm-and-air-defense-destroyers/.

[20] Ministère des Armées et des Anciens combattants, “LADA day : la FAN organise une journée dédiée à la lutte contre les drones aériens et de surface,” 30 June 2023, https://www.defense.gouv.fr/marine/actualites/lada-day-fan-organise-journee-dediee-lutte-contre-drones-aeriens-surface; Ministère des Armées et des Anciens combattants, “Wildfire : exercice de lutte contre les drones,” 8 April 2024, https://www.defense.gouv.fr/marine/actualites/wildfire-exercice-lutte-contre-drones.

[21] Thomas McMahon, “Navy Demonstrates First At-sea Reloading of Vertical Launching System,” America’s Navy, 15 October 2024, https://www.navy.mil/Press-Office/News-Stories/Article/3935108/navy-demonstrates-first-at-sea-reloading-of-vertical-launching-system/.

[22] Richard Scott, “US Navy set to trial VLS reloading system at sea,” Naval News, 19 February 2024, https://www.navalnews.com/naval-news/2024/02/us-navy-set-to-trial-vls-reloading-system-at-sea/#prettyPhoto.

[23] America’s Navy, “SECNAV Del Toro Delivers Remarks at the Future Warfighting Symposium,” 8 August 2024, https://www.navy.mil/Press-Office/Speeches/display-speeches/Article/3865157/secnav-del-toro-delivers-remarks-at-the-future-warfighting-symposium/.

[24] Ministère des Armées et des Anciens combattants, “Mission Akila : première expérimentation d’un transfert de missile Aster à la mer,” 14 May 2024, https://www.defense.gouv.fr/marine/actualites/mission-akila-premiere-experimentation-dun-transfert-missile-aster-mer

[25] Kai Greet, “French Navy Trials Ship to Ship Vertical Launch Missile Resupply,” The Aviationist, 27 June 2024, https://theaviationist.com/2024/06/27/french-navy-trials-ship-to-ship-vertical-launch-missile-resupply/.

[26] Nick Childs, “Navies and reloads: no silver bullet?,” International Institute for Strategic Studies, 23 October 2024, https://www.iiss.org/online-analysis/military-balance/2024/10/navies-and-reloads-no-silver-bullet/.

[27] Jacob Gronholt-Pedersen, “Danish frigate suffered weapon system failure in Red Sea combat, captain says,” Reuters, 4 April 2024, https://www.reuters.com/world/middle-east/danish-frigate-suffered-weapon-system-failure-red-sea-combat-captain-says-2024-04-04/

[28] Sebastian Sprenger, “Allies probe accidental targeting of US drone by German navy frigate,” Defense News, 29 February 2024, https://www.defensenews.com/global/europe/2024/02/29/allies-probe-accidental-targeting-of-us-drone-by-german-navy-frigate/.

[29] Jörg Stenzel and Michael Posey, “Analyzing the German Frigate Hessen’s Near-Miss of a U.S. Drone in the Red Sea,” Center for International Maritime Security, 7 May 2024, https://cimsec.org/analyzing-the-german-frigate-hessens-near-miss-of-a-u-s-drone-in-the-red-sea/.

[30] Sam LaGrone, “U.S. Super Hornet Shot Down Over Red Sea in Friendly Fire Incident; Aviators Safe,” USNI News, 21 December 2024, https://news.usni.org/2024/12/21/u-s-super-hornet-shot-down-over-red-sea-in-friendly-fire-incident-aviators-safe.