Michael Knights is the Boston-based Jill and Jay Bernstein Fellow of The Washington Institute, specializing in the military and security affairs of Iraq, Iran, and the Persian Gulf states.
The Houthis will likely try to intensify their cross-border missile strikes and other asymmetric tactics to internationalize the battle, steps the United States should firmly oppose.
This PolicyWatch is the third in a three-part series on the Red Sea campaign in Yemen. Part 1 covered the strategic risks and opportunities inherent in cutting off Houthi access to the sea. Part 2 looked at the operational challenges facing the two sides around Hodeida.
The Houthis have signaled that any effort to liberate Hodeida and al-Salif—the only deepwater ports they currently hold—could trigger a harsh response. Such measures are likely to include a surge of missile attacks into Saudi Arabia and possibly the United Arab Emirates, accompanied by efforts to disrupt the Red Sea and Bab al-Mandab Strait shipping lanes. Past incidents provide context:
On November 12, 2017, when the Gulf coalition briefly stopped all traffic to Houthi ports, the rebels threatened to attack Saudi tankers traversing the Bab al-Mandab Strait. The Houthi propaganda channel Al Masirah noted: "The battleships and oil tankers of the aggression and their movements will not be safe from the fire of [Houthi naval forces] if they are directed by the senior leadership [to attack]."
On January 9, 2018, the head of the Houthi political council, Saleh al-Sammad—who was later killed in an April 19 airstrike—threatened to block Red Sea shipping corridors if the coalition continued its advance toward Hodeida. "If the aggressors keep pushing toward Hodeida and if the political solution hits a wall, there are some strategic choices that will be taken as a no-return point, including blocking the international navigation in the Red Sea," Sammad was quoted saying on Al Masirah.
CROSS-BORDER ATTACKS ON THE GULF COALITION
Should the coalition intensify its offensive toward Hodeida, Houthi forces will likely respond by escalating cross-border attacks on Saudi Arabia and, possibly, the UAE's western desert. Key modes of attack could include:
Tactical rockets, drones, and short-range ballistic missiles. Such amplified bombardments would be very likely to target Saudi border towns, civilian airports, military bases, and industrial and oil complexes in Jizan, Najran, and other west coast locations. Such attacks will employ SS-21 Scarab B (OTR-21 Tochka) missiles, BM-27 multiple rocket launchers, the new Badr-1 extended-range rockets, and converted SA-2 SAM (called Qaher-1 and 2M by the Houthis) free-flight rockets. A Badr-1 was fired at Aramco's Jizan facilities on May 14. The Houthis are likely to supplement missile attacks with explosive unmanned aerial vehicles such as the Iran-supplied Qasef-1, which they used as recently as April 11 in an effort to hit Jizan's refinery.
Medium-range ballistic missiles. In addition to some remaining SS-1C/Hwasong-5 (Scud B) and extended-range SS-1D/Hwasong-6 (Scud C) missiles, the Houthis operate limited numbers of Iran-provided medium-range ballistic missiles that are extended-range versions of the Qiam-1 (called Burkan-2H by the Houthis). These missiles have struck Riyadh on three occasions since their introduction, and a surge of strikes on Riyadh might be initiated in an effort to intensify the crisis, bait the Saudis into harsh retaliation, and draw international calls for a ceasefire. Likewise, the Houthis might fire a Qiam-1 variant at the UAE's western borders to geographically broaden the war to a new country, a capability at which they have explicitly hinted. Houthi leader Abdul-Malik al-Houthi claimed on September 14, 2017, that the UAE was "now within range of our missiles," and the Houthis may well be able to land a missile in the UAE western desert following further adjustments to payload, materials, and fuel.
Terrorist attacks. The Gulf coalition has claimed that captured intelligence materials show that the Houthis may be preparing to undertake terrorist-type strikes in cities in Saudi Arabia, including assassinations and storming attacks on government locations.
DESTABILIZING THE RED SEA AND BAB AL-MANDAB
The Houthis control about 560 km of Red Sea shoreline between al-Khokha and Midi, including numerous islands, an Iranian "mother ship" (the Saviz) moored off the Dahlak Archipelago, the ports of Hodeida and al-Salif, and the oil-loading terminal at Ras Isa. From these bases, the Houthis have mounted scores of attacks on coalition bases in the Red Sea, on coalition shipping routes, on Red Sea international sea-lanes, and at the Bab al-Mandab choke point—a vital provider to the European energy market. Handling roughly four million barrels of oil per day, the strait is the next most important after Hormuz and Malacca. Proven Houthi antiship techniques have included:
Antiship missile attacks. The former Yemeni navy is known to have had P-21 "Styx II" (and its HY-2 Chinese version) and C-801 antiship missiles in its inventory. The Houthis debuted their antiship missiles by targeting an Emirati Swift-1 naval-support catamaran near the northern entrance to the Bab al-Mandab on October 1, 2016, using what Houthis claimed to be a C-802 antiship cruise missile. In 2016, the USS Mason was attacked on October 9, 12, and 18 by an unknown type of Houthi-operated antiship missile. The Houthis are conserving their remaining missiles and coastal radars following U.S. and Gulf coalition retaliatory strikes that targeted Houthi coastal radars in late 2016. To overcome this weakness, the Houthis now compel the use of maritime radars onboard moored vessels in Hodeida and al-Salif ports and have intelligence support from the Iranian "mother ship" Saviz and surveillance operatives on dhows in the Red Sea. Houthi coast-watcher teams have identification books showing Gulf coalition vessel profiles.
Fast-boat operations. The Houthis have undertaken a number of fast-boat attacks on Red Sea shipping, most recently a rocket-propelled grenade or tactical rocket attack on the Saudi double-hulled very large crude carrier named Abqaiq on April 3. The most spectacular attacks have included self-guiding Shark-33 explosive drone boats, which can be programmed to follow a course or home in on a target using electro-optical television guidance. Riyadh claims that such a device was used to strike a Saudi frigate on January 30, 2017, wounding at least five personnel. A Shark-33 variant was also used in an unsuccessful attack on a Saudi offshore loading facility in Jizan on June 16, 2017.
Naval mines placed in sea-lanes. The southward seasonal Red Sea drift between May and October draws mines released by the Houthis into the Bab al-Mandab. Indeed, mines have been located as far as 90 km southwest of Aden, having passed through the strait and into the Indian Ocean. The Houthis have made extensive use of indiscriminate naval mining tactics. According to the detailed annual report published by the UN Panel of Experts on January 26, 2018, forty-four naval mines were located in the Red Sea and the Gulf of Aden in 2017, of which four detonated. The experience of the Iran-Iraq War showed the limits of using mines against large double-hulled oil tankers, which can shrug off small Houthi improvised mines that carry only around 20 kg of explosives. Nevertheless, as a way of attracting international attention, affecting oil prices, and scaring off Red Sea shipping, the Houthis are likely to see deniable mining of sea-lanes as a profitable strategy.
Naval mines in anchorages and coastal approaches. The Houthis are also expected to mine the approaches to Hodeida in anticipation of a coalition assault from the sea. Most Houthi-operated moored contact mines are found at a depth of around five meters, which puts them in an unsuitable position to strike at any coalition naval vessel, except large replenishment ships, frigates, and patrol vessels—and thus civilian tankers as well. Now, however, the Houthis appear to be setting floating and moored mines to a depth of just two meters, possibly to target shallow-draft landing craft. The Houthis could also seed ports with bottom mines, and the coalition reportedly seized a number of bottom mines from Houthis near the port of Mokha that strongly resemble an Iranian model—displayed by the Islamic Revolutionary Guard Corps in 2015 as a 42 kg composite-aluminum limpet mine.
Combat diver operations. Houthi combat diver units outfitted in wetsuits have been receiving training on Red Sea coastal islands such as al-Bawadi. Instructional videos show trainees learning how to identify Saudi frigates and UAE corvettes. The IRGC Navy (IRGCN) and Lebanese Hezbollah both run naval combat diver groups capable of undertaking mining attacks on ships in harbor. For example, operating out of Faror island in the Persian Gulf, the IRGCN's Special Force (SNSF) is known to run the "axis of resistance" foreign diver training program.
Scorched-earth sabotage of ports. If the Houthis lose control of Hodeida, al-Salif, and Ras Isa, retreating Houthi forces might sabotage port facilities to deepen the humanitarian crisis in Yemen, counting on the likelihood that deterioration would be blamed primarily on the Gulf coalition. Even if the port is captured intact, the Houthis might also use rockets fired from nearby vantage points to complicate safe operation of the port.
RECOMMENDATIONS FOR U.S. POLICY
The United States should warn against and actively oppose asymmetric Houthi efforts to broaden or further internationalize the conflict. Intensified indiscriminate use of Iran-provided ballistic missiles against Gulf cities, potentially now including those in the UAE with sizable Western expatriate populations, is an outcome that must be prevented. To signal that such an escalation will not be tolerated, Washington should provide timely geolocations of missile launches to the Gulf coalition to maximize the chances of destroying the launchers, under existing authorities to assist allied states in their own protection using nonlethal aid. The United States should actively discourage any Saudi or UAE overreaction to missile attacks, as happened when Riyadh briefly closed all Yemen's ports after missile attacks on Riyadh in November 2017.
Likewise, intensified Houthi harassment of global shipping and the Bab al-Mandab Strait directly contradicts U.S. national interests regarding the free flow of trade and the security of vital sea-lanes. As part of its global "duty to warn" authorities, the United States should actively work with the UN-backed Yemeni government and the coalition to immediately and publicly expose any Houthi naval mining operations or other reckless attacks that endanger global shipping. As with ballistic missile launches, the United States should engage in a timely exchange of warning and geolocation data regarding antiship missiles, fast-attack boats, and other maritime strikes that might endanger shipping. The Iranian "mother ship" in the Red Sea should be closely monitored to ensure it is not facilitating maritime attacks through providing targeting data on the movement of shipping boats.
Most important, the sabotage or destruction of port facilities and naval mining of harbors will complicate and delay the restoration of humanitarian inflows to Yemen's most populated areas. Washington should maintain a very close watch on both coalition and Houthi operations during the Hodeida campaign, and should quickly speak out if either party appears to be deliberately inflicting damage on port facilities and harbors. U.S. officials should strongly encourage the UN special envoy for Yemen, Martin Griffiths, humanitarian agencies, and UN member states to signal to the Houthis that rebel forces will be viewed as responsible for undertaking scorched-earth tactics or firing rockets on the port, should they engage in such activity, and to caution the Gulf coalition against targeting port facilities.
The United States should also warn the Iranians, the primary suppliers of arms to the Houthis, that it will view them as complicit if they fail to restrain the Houthis from using scorched-earth tactics or otherwise broadening the war using Iranian armaments. There is ample legal justification for issuing such a warning. After examining Iranian missiles fired into Saudi Arabia from Yemen, the January 2018 UN Panel of Experts report concluded that "the Islamic Republic of Iran is in non-compliance with paragraph 14 of resolution 2216 (2015)," referring to the UN arms embargo imposed on the Houthis under Chapter VII of the UN Charter.
Farzin Nadimi is an associate fellow with The Washington Institute, specializing in the security and defense affairs of Iran and the Persian Gulf region. Michael Knights, a senior fellow at the Institute, recently returned from a visit to Yemen's battle fronts, where he received detailed briefings from Yemeni and Gulf coalition officers on Houthi naval tactics and weaponry.