Jeremy Vaughan, a commander in the United States Navy, was a 2016-2017 military fellow at The Washington Institute.
Reenergized and more-targeted maritime interdiction operations could reduce Iranian support for the Houthis while helping respond to Yemen's humanitarian crisis.
For nearly ten months, the war in Yemen has periodically spilled into the Red Sea, degrading maritime security in the basin. To date, Houthi attacks have primarily targeted Saudi Arabia, the Emiratis, and those perceived by the rebels to be in the Saudi-led coalition, using antiship cruise missile attacks and explosive "drone boat" attacks. Sophisticated weapons wielded by nonstate actors and increased mining activity increase the risk that the conflict could disrupt freedom of navigation and commerce through the Red Sea and the Bab al-Mandab (BAM) Strait, an important energy waterway. Saudi Arabia and the United Arab Emirates have suggested that seizure of Hodeida, Yemen's most important shipping port, would cut off Houthi rebel access to the sea and mitigate this risk.
Meanwhile, the potential for a famine of significant proportions is building in Yemen. Coalition efforts thus far to constrain Houthi activities and Iranian weapons smuggling in the Red Sea and the BAM are perceived to be acting as more of a blockade -- slowing the flow of food, medicine, and fuel into Yemen, and deterring some shippers from sending their vessels into Yemeni ports. Considering that Yemen imports 90 percent of its food, many experts warn that recapture of Hodeida would ultimately cut off what food is currently trickling into the beleaguered nation, tipping it fully into famine.
A reenergized and more targeted maritime interdiction operation (MIO) -- one supported and facilitated by the United States through intelligence sharing, training, and coordination -- could be used to disrupt Iranian weapons smuggling and increase the flow of food, medicine, and fuel into Yemen. Given the continuing conflict, the risk of famine, and the accelerating cholera outbreak -- reported to have recently passed 300,000 suspected cases -- both are urgent goals.
Recent Houthi Attacks on Coalition Maritime Targets
Since the Yemen conflict began in March of 2015, Houthi rebels have attacked coalition or coalition-affiliated maritime targets four times (a UAE HSV-2 Swift in October 2016; the Al Madinah, a Saudi frigate in January 2017; a Yemeni coast guard ship in March 2017; and a seaside Saudi Aramco facility in April 2017), an American ship twice (both in October 2016), and other shipping twice more (June 2017). The United States responded to the attacks on its ships with a combination of diplomacy and calibrated military strikes against three radar facilities in Houthi-controlled territory. Since October, no further attacks have targeted U.S. ships.
Advantage of Maritime Interdiction Operations over a Blockade
During MIOs, a naval force monitors access to waterways and interdicts specific ships, while allowing or even ensuring the free flow of legitimate maritime commerce. To execute MIO, naval forces build a network of surveillance, intelligence, and interdiction forces whose enforcement operations divert, disrupt, delay, or seize contraband items. Interdiction operations often compel a smuggling network to change and communicate about those changes, making it even more vulnerable to further disruption. The MIO efforts in the Arabian Gulf (1991-2003) demonstrated tangible effects. Although resource-intensive and dangerous at times, this MIO slowed Iraqi president Saddam Hussein's attempts to rearm following the 1991 Gulf War.
Already limited maritime operations adjacent to and near Yemen to enforce UN Security Council resolutions (UNSCRs) that prohibit arms transfers to Yemen (UNSCR 2216, OP14-17) and arms transfers from Iran (UNSCR 2231, Annex B, 6(b)) have resulted in some interdictions. In 2015, U.S. and Australian ships boarded the Nassir, a ship filled with antitank weapons systems sourced from Iran. In February 2016, the HMAS Darwin seized Iran-sourced weapons from a dhow -- a small fishing vessel -- headed toward Yemen. A month later, French and U.S. naval forces boarded dhows on separate occasions and found Iranian arms shipments bound for Yemen. These opportunistic interdictions suggest that a fully implemented MIO to halt arms transfers to Yemen could be productive.
A strengthened MIO offers an avenue to improve security in the Red Sea without risking U.S. boots on the ground. Similarly, nations hesitant to intervene directly will more likely be willing to enforce UN Security Council resolutions through MIO. In addition, transforming what is perceived to be a blockade into an interdiction operation and accelerating the flow of food could reduce key drivers of the conflict, while increasing the legitimacy of the coalition's naval effort. Lastly, intelligence gained through interdiction of illegal arms shipments could more tightly link Iran to such arms shipments, providing the international community greater leverage when dealing with the Islamic Republic.
Nonetheless, as noted, sustainment of a traditional MIO effort is resource-intensive. From an outsider's perspective, MIO can seem as simple as a police checkpoint, but it is much more complex. For example, Operation Iraqi Freedom's maritime forces conducted 5,000 queries, carried out 2,600 boardings, and diverted 400 ships for searches. Effective MIOs require warships, intelligence, surveillance, and reconnaissance (ISR), coalition coordination, and training. The sheer size of the waterspace demands that maritime interdiction start with a heavy ISR down payment to establish a baseline. Potential arms smugglers are then monitored, boarded under international law, and searched. Intelligence gained through the ship searches is fed back into the system to make subsequent operations more effective. Given the number of ships required to sustain MIO, and that the operational cost for a frigate-sized ship can be upward of $1.3 million per month, the bill can be significant. Operation Atalanta, the EU effort to combat piracy in the Gulf of Aden, cost around $450 million in 2009.
There are also important force-protection risks to consider. When a potential smuggler is intercepted, it must be boarded and searched by a warship in close proximity. If the suspected vessel does not cooperate, boarding teams could face anything from passive measures to small arms and fire hoses. If a ship is seized, the "prize crew" of sailors taking it over could face an adversarial crew or a structurally unseaworthy ship. Tragically, members of a U.S. Navy prize crew perished in 2001 when the decrepit ship they boarded sank. In addition, as smugglers tend to hug the coast, MIO efforts are likely to draw naval forces closer to shore, increasing the risks of Houthi-led or directed attacks using coastal-defense cruise missiles, mines, or unmanned explosive boats.
The United States could offer to support a more effective MIO in and around Yemen in order to prevent additional arms from flowing into Yemen, and to accelerate the flow of food, medicine, and fuel into Yemen's Red Sea ports.
Existing Security Council resolutions (UNSCRs 2216 and 2231) offer a viable legal regime for such maritime interdictions. This legal framework provides a mechanism for searching most vessels in international waters. In addition, the internationally recognized government of Yemen, led by President Abdu Rabu Mansour Hadi, can inspect a vessel en route to a Yemeni port once it enters the nation's territorial waters (by definition, this excludes innocent passage). In April and May 2015, Iranian attempts to deliver cargo to Hodeida with Iran-flagged vessels and armed naval escorts were effectively blocked by the U.S. Navy. Following this, in order to deter future military confrontations on the high seas, the United Nations created the Inspection and Verification Mechanism (UNVIM) to review and inspect, if necessary, ships carrying goods into Yemen's Red Sea ports. This mechanism was put in place on the basis of an August 6, 2015, request by the Yemeni government. However, for operational reasons, UNVIM does not review or inspect ships 100 metric tons and below. These smaller ships and dhows are favored by arms smugglers in the Arabian Sea for carrying Iranian weapons.
The United States could provide a range of support to help the Saudi-led coalition strengthen its interdiction operations off the coast of Yemen. Such potential measures include increased ISR, increased intelligence-sharing, training for cooperative and opposed boardings/inspections, and coordination assistance. This U.S. support could reenergize and, just as important, redefine the coalition's maritime interdiction operations around Yemen to focus on smaller cargo ships and dhows.
Internationalizing this effort could intensify pressure on Iran to reduce its arms smuggling to Yemen and on the Houthis to abstain from further attempts to interfere with maritime traffic around Yemen and the BAM. Saudi Arabia's other international partners could also provide additional ISR, training, coordination support, and intelligence sharing. A Combined Task Force construct, already in use for counterterrorism (CTF-150), counterpiracy (CTF-151) and Gulf maritime security (CTF-152), would provide a familiar structure for the problem of security in waters surrounding Yemen and ensure that each nation is only assigned duties it is willing to conduct, while still leveraging the strengths of each navy. For its part, the NATO Maritime Interdiction Operational Training Centre in Souda Bay, Crete, provides advanced classroom and practical MIO instruction, attended already by small numbers of Gulf military students. Increasing the enrollment at the Centre could immediately improve MIO tactics and potentially help develop a long-term maritime-interdiction capacity. Maritime partners from Europe, joined by others such as Australia, India, Pakistan, and South Korea on a voluntary, rotational basis, could share the MIO load while sending a strong statement to Iran.
Benefits -- and Risks -- of Enhanced U.S. Involvement
Increased U.S. support could advance national interests in several ways. First, U.S. involvement could identify additional Iranian efforts to deliver weapons and other military assistance to the Houthis. Second, a U.S. presence -- even if not on the MIO's picket line -- could help deter smuggling ships from entering the area. Third, American involvement could give legitimate shippers reassurance and confidence that delivering food and medicine into these ports will not be disrupted. Fourth, by focusing coalition efforts on a narrower target set, U.S. coordination assistance could help accelerate the delivery of shipments to Yemeni ports.
Providing such support, of course, carries risks for the United States. A stronger maritime-interdiction effort without a parallel effort to address reports of overland smuggling could expend a large naval resource investment without achieving a reduction in the overall flow of arms. Second, if dhows draw MIO warships within range of coastal weapons systems, they could, as noted, sustain increased attacks. The greatest risk would be that the United States is accidentally or intentionally drawn further into the broader Yemen conflict. Indeed, the Houthis or Iranians may seek to involve the United States more directly in the war to further polarize the conflict, thereby expanding support for their side within Yemen and beyond. A limited seaborne attack on a U.S. warship could be an accelerant for more direct U.S. military involvement. Finally, if the coalition received expanded international support, the capabilities gap between coalition and Western navies could create an insatiable demand for U.S. ships and personnel, presenting the very real risk of mission creep. Without conscientious efforts to maintain predetermined levels of burden sharing, the more effective forces will end up shouldering more of the MIO burden.
In sum, a reenergized and more targeted MIO -- one supported and facilitated by the United States -- appears worthy of consideration. It could help reduce maritime threats in the Red Sea and decrease shipping disruptions between the Red Sea and the Strait of Hormuz, both U.S. core interests. U.S. support could be designed to surge initially in order to enable more precise and effective coalition interdictions and then be drawn down as soon as coalition forces are more capable of carrying out the improved MIO. Refining and strengthening the coalition's efforts could help deter the flow of Iranian weapons that is helping feed the conflict, while seeking to increase significantly the flow of food, medicine, and fuel to a desperate Yemeni population.
Eric Pelofsky is an adjunct fellow at The Washington Institute who served as special assistant to the president and senior director for North Africa and Yemen at the National Security Council from 2014 to 2017. Cmdr. Jeremy Vaughan, U.S. Navy, is a Federal Executive Fellow at The Washington Institute who has completed multiple deployments to the Persian Gulf. The views expressed herein are those of the authors and do not reflect the official policy or position of the U.S. Navy, U.S. Department of Defense, or U.S. government.