Iranian Threats to Gulf Maritime Security

Following Trump administration warnings regarding pending Iranian attacks, four commercial vessels were damaged last weekend in the Gulf. While details remain murky, this development underscores how Tehran and its proxies may exploit maritime vulnerabilities in the region.

Tehran has a history of targeting civilian vessels transiting the Gulf and threatening to close the Strait of Hormuz, through which approximately one fifth of the world’s seaborne oil passes. During the last two years of the Iran-Iraq War, Iran conducted 143 attacks against shipping in the Gulf. Last month, Islamic Revolutionary Guard Corps Navy (IRGCN) Commander Rear Admiral Alireza Tangsiri threatened to close the strait.

This month, tensions escalated when the U.S. reportedly obtained intelligence that Iran, among other steps, was putting missiles on small boats in the Gulf – fueling fears that the IRGC might use them to attack commercial vessels or U.S. Navy ships.

To avoid international condemnation and direct confrontation with the United States military, Tehran may use covert operators to conduct attacks. This could include the use of divers or crew members to sabotage vessels. Such an approach would be consistent with Tehran’s use of proxies and asymmetrical terrorist attacks. Such tactics enable Tehran to achieve its objectives at a relatively low cost, while evading attribution and consequences.

In contrast to sabotage operations, an effort to close the Strait of Hormuz, or severely impede passage through it, would likely require the robust and overt use of Tehran’s two distinct naval forces: the IRGCN and the Islamic Republic of Iran Navy (IRIN). According to the U.S. Office of Naval Intelligence (ONI), the IRGCN deploys “smaller, faster platforms equipped with sophisticated weaponry, ideally suited for its asymmetric doctrine.” Leading acquisition priorities for the IRGCN have included “fast attack craft, small boats, anti-ship cruise missiles, and mines.”

For years, the IRGCN used these fast attack craft and small boats to harass U.S. Navy vessels. ONI assesses that the IRGCN believes it can prevail in the confined Gulf waters by using its weapons and systems “in unexpected ways to achieve tactical surprise,” including so-called “swarm” attacks of small boats and anti-ship missiles, which could present tactical complications for the U.S. Navy.

The IRIN, meanwhile, employs a more conventional doctrine. According to ONI, the IRIN has “undertaken a major recapitalization program to replace its aging surface fleet and augment its submarine force.” In a potential conflict in the strait, one could expect the IRIN to employ its surface ships, mines, coastal defense cruise missiles, and aviation assets. The IRIN would also likely utilize its attack submarines, most of which Tehran procured from Russia and North Korea. The IRIN’s submarine fleet can attack ships with torpedoes and mines and serve as special operations platforms.

Given Tehran’s long history of terrorism and harassment in the Gulf – as well as the regime’s recent threats and military exercises – Iran may escalate attacks on maritime traffic in the Gulf and Strait of Hormuz.

As history suggests, the best way to deter such attacks is for the United States to signal clearly and credibly that it will meet Iranian aggression – asymmetrical or conventional – with a decisive response. This was the likely message the administration was trying to send with the recent deployment of increased U.S. combat power to the Gulf – including the arrival Thursday of two U.S. guided-missile destroyers. Whether the radical regime in Tehran gets the message remains to be seen.

Bradley Bowman is senior director for the Center on Military and Political Power (CMPP) with the Foundation for Defense of Democracies (FDD), where Andrew Gabel is a research analyst. Follow Bradley and Andrew on Twitter @Brad_L_Bowman and @Andrew_B_Gabel. Follow FDD on Twitter @FDD and @FDD_CMPP. FDD is a Washington, DC-based, nonpartisan research institute focusing on national security and foreign policy.