Cluster Bomb Toting F-15Es Are Patrolling The Persian Gulf To Counter Small Boat Swarms

The weapons would be a useful tool for destroying Iran’s fast boat armada that it has used to seize and harass tankers.

byJoseph Trevithick|
Cluster Bombs photo


U.S. Air Force F-15E Strike Eagles have been flying patrols over the Persian Gulf armed with cluster munitions, as well as a variety of other weapons. These weapons could be useful for beating back swarms of small boats, such as those belonging to Iran's Islamic Revolutionary Guard Corps, IRGC. The sorties come amid escalating tensions between the United States and Iran, as well as the IRGC's harassment and seizure of a number of tankers in Strait of Hormuz in recent weeks.

Images emerged of the cluster munition-armed F-15Es on July 31, 2019, as part of an official news item from the 380th Air Expeditionary Wing about the Surface Combat Air Patrols, or SuCAP. The 380th is the Air Force's main unit at Al Dhafra Air Base in the United Arab Emirates. The Strike Eagles, assigned to the 336th Expeditionary Fighter Wing, had arrived there in June.

"Their [the F-15Es'] role is to conduct combat air patrol missions over the Arabian Gulf and provide aerial escorts of naval vessels as they traverse the Strait of Hormuz," the official news item explained. "The F-15E is a dual-role fighter designed to perform air-to-air and air-to-ground missions and is currently conducting Surface Combat Air Patrol (SuCAP) operations to ensure free and open maritime commerce in the region."

Accompanying pictures show the jets conducting SuCAPs on multiple occasions since June 2019. Pictures show at least some of the aircraft carrying Wind Corrected Munition Dispensers (WCMD), a GPS-assisted inertial navigation system guided canister that can carry a number of different cluster munitions. There are different designations for WCMDs loaded with different submunitions.

An F-15E sits at Al Dahfra Air Base in the United Arab Emirates ahead of a Surface Combat Air Patrol in July 2019. Three WCMD cluster munitions are visible on the aircraft's lefthand fuselage stations., USAF

We can see the particular markings on these cluster munitionss, but for overwater missions, it is unlikely they are CBU-104/Bs, which contain dozens of Gator anti-personnel and anti-tank land mines. The other two main types of WCMD bombs in U.S. military inventory are the CBU-103/B, with a load of 202  BLU-97/B Combined Effects Bomblets (CEB), or the CBU-105/B, also known as the Sensor Fuzed Weapon (SFW), with 10 BLU-108/B Sensor Fuzed Munitions (SFM).

A member of the US Air Force prepares WCMDs for loading onto F-15Es ahead of a Surface Combat Air Patrol in July 2019., USAF

The BLU-97/B is a traditional cluster sub-munition. It weighs just shy of three and a half pounds and has fragmentation, anti-armor, and incendiary effects, giving it the capability to take out a wide array of different targets. The SFM is a larger and much more complex, smart munition and each one has four separate anti-armor warheads with their own infrared and laser sensors to spot targets and destroy those targets with pinpoint accuracy. You can read more about the complete CBU-105/B in detail here.

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Either submunition could be useful against swarms of small boats, but the SFW would seem to be uniquely suited for the mission. Iran has used its relatively giant small boat fleet in recent months to harass and seize foreign commercial ships, which generally offer limited protection for their crew. Damage to engines, weapon systems, or crew, could easily achieve a mission kill even if the craft remains afloat.

All this being said, cluster munitions have become increasingly controversial in recent years, despite their continuing military utility, and the U.S. government had sought to increasingly restrict their use and steadily eliminate them from U.S. military inventories. In 2017, President Donald Trump's Administration reversed course, deciding to retain existing stockpiles of cluster munitions for the time being, though the development of alternative weapons has continued. You can read more about the international debate about these weapons and U.S. policy toward them in this past War Zone feature.

Beyond the cluster munitions, the released pictures show that Strike Eagles from the 336th have been ready to take on individual moving targets with laser-guided bombs, as well. In one case, a pair of F-15Es each carried at least two 500-pound class GBU-12/B Paveway II bombs and one of them had a 2,000-pound class GBU-24/B Paveyway III on its centerline station. The latter weapon is capable of disabling or destroying any ship in the Iranian Navy.

Two F-15Es from the 336th Expeditionary Fighter Squadron conduct a Surface Combat Air Patrol in June 2019. The jet on the left is carrying cluster munitions, while the other has a GBU-24/B on its centerline pylon., USAF

In addition, the F-15Es each carried a pair of AIM-120C Advanced Medium-Range Air-to-Air Missiles (AMRAAM) and two AIM-9X Sidewinder short-range infrared homing missiles. These weapons offer a self-defense capability, but could also allow them to engage other aircraft, including drones, that might be threatening other U.S. or other friendly forces, as well as commercial ships. In 2017, Strike Eagles flying over Syria shot down two Iranian unmanned aircraft, on separate occasions, which appeared to be targeting American troops and their local partners. 

We have also seen Air Force F-15C Eagles and F-35A Joint Strike Fighters armed with air-to-air missiles flying in the region in recent months. It's also worth noting that the AIM-9X, with its imaging infrared seeker, can engage maneuvering surface targets, like fast boats. 

None of the F-15Es flying SuCAPs appear to have been carrying the AN/ASQ-236 Dragon's Eye Active Electronically Scanned Array (AESA) radar pod, but we do know that the 336th brought a number of these advanced sensor systems with them when they deployed earlier in July. Dragon's Eye is primarily a radar imaging system, but can reportedly also provide ground-moving target indicator (GMTI) data to target vehicles on land and ships at sea.

F-15Es from the 336th at Al Dahfra Air Base in June 2019. Five of the six aircraft in the foreground are carrying Dragon's Eye radar pods., USAF

The 336th has also already been training to integrate with U.S. Navy aircraft and ships, which could also feed targeting information to the F-15Es. On July 24, 2019, a pair of the squadrons Strike Eagles took part in an exercise in the Persian Gulf that included the Arleigh Burke class destroyer USS Gonzalez and a P-3C Orion maritime patrol plane.

"The P-3C provides maritime domain awareness, can also function as a maritime air controller with long loiter times, or employ its own weapons as required," U.S. Navy Lieutenant Commander Adrian Willing, the Master Air Attack Plan Cell planner within the Air Force's 609th Air Operations Center at Al Udeid Air Base in Qatar, said in a statement. "The USS Gonzalez is operating in the Arabian Gulf to guarantee international freedom of navigation."

The Air Force has already begun to focus more on how it might respond to the threat of small boat swarms in recent years. In 2017, A-10 Warthogs conducted an exercise in the Gulf of Mexico involving just this sort of scenario.

The appearance of the F-15Es in the Persian Gulf flying these sorts of patrols now is not particularly surprising. Since May 2019, the U.S. military has been sending a steady stream of additional assets, including combat aircraft, ships, and other personnel, to the region in response to still largely undefined intelligence warning of increased threats to American interests from Iran and its proxies.

The Strike Eagle, with its robust range and good loiter time, combined with its large payload capacity and multi-mission capabilities, is an ideal tool for conducting SuCAPs in the region. Having the Weapon Systems Officer (WSO) is also really useful for dynamic operations. The mix of weapons on the aircraft in the pictures the Air Force has released only further underscores just how flexible a platform the F-15E is, in general.

On on July 19, 2019, U.S. Central Command had also formally announced the start of a new maritime security mission dubbed Operation Sentinel. This was the same day that Iran seized the British-flagged tanker Stena Impero using a combination of forces aboard small boats and an Mi-17 helicopter. Iran had threatened to do just this following the United Kingdom's seizure of the Iranian supertanker Grace 1 off the coast of Gibraltar on July 4.

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Iran had already harassed another British-flagged tanker, the British Heritage, seized a Panama-flagged tanker Riah

on still-murky charges of fuel smuggling, and is linked to a spate of outright attacks on commercial ships across two separate incidents in May and June 2019. The IRGC also shot down a U.S. Navy drone in June that almost prompted U.S. military strikes on Iran and, more recently, the U.S. Navy said that U.S. Marines on the amphibious assault ship USS Boxer had knocked down at least one Iranian unmanned aircraft over the Strait of Hormuz using an electronic warfare system.

Despite all this, Operation Sentinel remains very much a work in progress. "We will escort our ships as they come along, but we won't be there in great numbers," U.S. Navy Vice Admiral Michael Gilday, who is set to be the next Chief of Naval Operations, said during his confirmation hearing on July 31, 2019.

"The coalition that we're building in the Arabian Gulf and specifically in the Strait of Hormuz is going to be a 80- or 90-percent coalition effort," Gilday continued. "A much smaller U.S. effort is primarily focused on providing intelligence support to the rest of the coalition."

A US Navy MH-60R Sea Hawk helicopter flying from USS Boxer in the Strait of Hormuz, at right, escorts an Iranian Navy Bell 212 helicopter, at left, away from US ships during an incident on July 18, 2019., USN

The United Kingdom had proposed a separate, European-led mission last week, but this effort appears to have been muted since the country's new Prime Minister Boris Johnson took office on July 24, 2019. Johnson is seen as friendlier toward U.S. President Donald Trump than his predecessor Theresa May and he could be looking reassess the U.K. government's cooperation with the United States on maritime security in the Middle East, as well as policy toward Iran more generally.

The United States has had trouble otherwise finding willing partners to join its maritime coalition, with the German government recently saying it would not particpate. On July 31, 2019, it emerged that the United Arab Emirates, a major American partner in the region, had actually sent a delegation to Iran to discuss the security situation.

"We are gonna keep it open," U.S. Secretary of State Mike Pompeo had declared during a talk on July 29, 2019. “We are going to build up a maritime security plan. Countries from all across the world who have a vested interest in keeping those waterways open will participate."

So, at least for the foreseeable future, cluster munition-toting F-15Es, along with other U.S. military assets, look set to continue patrolling region's waterways.

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