By Anthony Cordesman, Center for Strategic and International Studies–

The events in Iran and the Gulf during the last week have been a grim reminder that Iran remains the major threat to U.S. strategic interests in the Gulf and the Middle East, and that General James Mattis has been all too correct in singling out Iran as such a threat. Islamist extremism and terrorism are very real threats—but they are limited in scope and lethality.

In contrast, Iran has the ability to trigger a major war in the region, and to threaten the world’s main source of oil and gas exports—the 17 million barrels of oil a day that flow through the Strait of Hormuz. Any such Iranian action threatens the stability of the entire global economy, the global (and U.S. domestic) price of oil and of transportation fuels, and the import and export capabilities of America’s key trading partners in Asia—more than a third of U.S. manufactured imports.

There is nothing theoretical about this threat. On January 8, four Iranian Revolutionary Guards fast patrol boats came within 900 yards of the U.S.S. Mahan, a guided missile destroyer that was providing an escort to an amphibious warship with 1,000 Marines on board, and a Navy oiler making passage through international waters in the Gulf. They were heading directly towards U.S. vessels, and the U.S.S. Mahan had to fire warning shots to keep them at safe distance. Moreover, this is only the latest incident in a sustained pattern of harassment and provocation in the Gulf. The New York Times reports that there were 35 close encounters between American and Iranian vessels in 2016, most of which occurred during the first half of the year, and 23 encounters in 2015.


This is a grim reminder of the fact Iran has threatened in the past to close the Gulf to all shipping traffic, and is steadily building up a mix of naval, missile, and air capabilities to threaten shipping traffic all along its Gulf coast, at the Strait, and outside in the Gulf of Oman. This is not posturing or some casual series of incidents. Iran is steadily building up its submarine and submersible capabilities, land/sea/air based anti-ship missile forces, ability to rapidly deploy smart mines, and ability to “swarm” with missile-armed patrol boats and high speed craft armed with explosives that can be used for suicide attacks. At the same time, it is expanding its activities in the Indian Ocean.

The Iranian military threat also goes far beyond action against combat ships and shipping in the Gulf, and is described in detail in a recent CSIS study entitled Iran and the Gulf Military Balance ( The JCPOA nuclear agreement has forced Iran to dismantle or limit the capability of some key nuclear facilities, but no arms control agreement can ever really bind the future. The agreement has not affected Iran’s ability to develop more advanced centrifuges or to carry out a wide range of covert low-level nuclear weapons development activities.

More importantly—at least as long as the present nuclear agreement holds—Iran is steadily building up a massive mix of long-range artillery rockets, ballistic missiles, and cruise missiles, and developing the ability to arm them with precision-guided conventional warheads. If Iran succeeds in creating a large force of truly accurate missiles, it can go from weapons of mass destructiveness to weapons of mass effectiveness—targeting critical petroleum, desalination, power, and military facilities in the Gulf, and even Israel and Egypt.

If Iran can obtain more truly advanced weapons systems like the S-300 anti-air missile system it has bought from Russia, and like its most advanced Chinese anti-ship missiles, it can also alter the balance in every aspect of conventional warfare. Iran has made its interest in such purchases all too clear, it has shown it can work with Russia in Syria, and Russian restraint is—to say the least—unpredictable.

Iran has also been all too successful in increasing its military strategic influence in the region. It has worked with Syria to give the Hezbollah in Lebanon a massive set of rocket and missile forces far larger than the one Hezbollah had in 1982, one that includes at least some precision-guided systems. Iran has aided the Hezbollah in becoming a major force in Syria as well as providing its own advisors, volunteers, arms, and money to Assad.

Iran largely ceased attacking Americans in Iraq after General Mattis took the lead in pressing for a strong U.S. reaction and threatening to retaliate in 2011. Since that time, however, Iran has steadily built up its influence and its military role in Iraq since, has put advisors at many different levels with Iraqi security forces and militias, has played a major role in arming and training Iraq’s large Shi’ite Popular Militia Forces (PMFs), and has used the Hezbollah as its proxy in gaining influence over the PMFs.

Less than seven days ago, the Long War Journal reported that, [ii]

Abu Mahdi al Muhandis, the deputy commander of the Iraq’s Popular Mobilization Forces (PMF), gave an in-depth interview last week with the pro-Iranian, pan-Arab satellite television channel Al Mayadeen, in which he confirmed the presence of Lebanese Hezbollah in Iraq. In the interview, Muhandis said that there was a “very good” relationship between his PMF and Hezbollah, carried out with “the knowledge and agreement” of the Iraqi government. He said that both Prime Minister Nouri al-Maliki and Haidar al-Abadi were aware of the relationship from the outset, “down to the minute details.”

He said that PMF “benefited greatly” from Hezbollah’s support, who played a “central” and “very important” role in the PMF’s battle-readiness. Muhandis said “the brothers in Hezbollah” sent advisors to Iraq from the beginning of the battles against ISIS. Along with Iran, Hezbollah helped the PMF “with training and planning, and with weapons and equipment.” However, he also hinted that Hezbollah’s role may not have been exclusively advisory, saying that the Lebanon-based Shiite group “offered martyrs” on Iraq’s battlefields.

It is all too clear that once the United States helps Iraq defeat ISIS, Iran will have every incentive to try to push the United States out of Iraq, and dominate at least the Shi’ite side of Iraqi politics and security forces. It is equally clear—as General Mattis warned very clearly during his time as commander of USCENTCOM—that the United States is no bystander in the confrontation between Iran and Saudi Arabia, the UAE, and other Arab states. Moreover, Iran plays an active role in the Sunni and Shi’ite tensions in Bahrain, Kuwait, and Yemen as well.

The United States also received a third warning with the same week. The sudden death of Ayatollah Akbar Hashemi Rafsanjani on January 8th was a yet another further step in a pattern of Iranian internal politics that make it steadily less likely that Iran’s present Supreme Leader—the Ayatollah Ali Khamenei—will be replaced by anyone more moderate. Equally, this pattern makes it steadily less likely that Iran’s President Hassan Rouhani can temper the hardline posture of Khamenei and the Iranian Islamic Revolutionary Guard (IRGC), or temper the hardliner ability to dominate every aspect of Iran’s security posture.

Rafsanjani had evolved to be a key protector of moderate political figures in a country where being “moderate” may be a relative categorization, but is still all too dangerous. The United States may deserve some blame for not properly exploiting the opportunities created by the nuclear agreement, but Iran’s internal politics—and its present Supreme Leader—have made it all too clear that the nuclear agreement was forced upon Iran and the Supreme Leader, and the IRGC remain as hawkish as ever.

Both President Trump and both sides of the aisle in the Senate and House should remember these facts about the Iranian threat as they reexamine U.S. strategy and security policy at the start of a new Administration. They should remember that U.S. energy independence will only exist in terms of all forms of energy—and that the United States will remain dependent on imported oil.

More immediately, they should remember just how correct General Mattis has been in focusing on the Iranian threat as well as on terrorism and on the other threats in the region, how important his efforts to create strategic partners out of Israel and Arab states have been, and that—while he may not have had the full support of the White House—both the then Secretaries of Defense and State supported more decisive U.S. action.

The United States badly needs a Secretary of Defense with a proven ability to think strategically and develop real world plan for action, with a proven focus on joint warfare and not a single service, one who knows how to manage resources effectively, who sees the value of strategic partners, and will seek both decisive and proportionate action. We really need the best Secretary of Defense we can get, and not only because of the Middle East and the Gulf.

[i] Michael A. Gordon, “American Destroyer Fires Warning Shots at Iranian Boats,” New York Times, January 9, 2017,

[ii] David A.Daoud, “PMF deputy commander Muhandis details Hezbollah ops in Iraq,” Long War Journal,” January 9, 2017,

Anthony H. Cordesman holds the Arleigh A. Burke Chair in Strategy at the Center for Strategic and International Studies (CSIS) in Washington, D.C.

Commentary is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

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