As activity in the Red Sea has heated up this month, debate rages on in Washington about Tehran’s role in attacks against U.S. forces there. The Pentagon confirmed this month that the Iranian-backed Houthi rebels in Yemen were responsible for launching cruise missiles at the USS Mason on Oct. 9 and 12, while it still investigates a potential third attack on Oct. 15. The confirmed attacks, which prompted U.S. strikes against Houthi installations on the coast, were reportedly in retaliation for U.S. backing of the Saudi-led coalition aimed at expelling them from the capital.

It is not definitively known whether Iran supplied the missiles, but the motives are clear as to why they would have supported the attack.

Iran’s Islamic Revolutionary Guard Corps (IRGC) and Hezbollah have provided the Houthis with money, training, advising, and sophisticated weaponry for more than a decade, according to the State Department’s Country Reports on Terrorism 2012 (though that language was dropped in 2015). The Guard is believed to have transferred rocket and missile capabilities, as well. The US and its allies have intercepted five shipments from Iran to the Houthis since April 2015 that have included coastal defense systems, according to a senior U.S. official who spoke with NBC News. Tehran has stepped up its assistance since May 2016, sending anti-ship missiles, explosives, and personnel through Oman, according to Reuters, who spoke with Western and Iranian intelligence officials.

Some senior U.S. defense officials say the missile system used against U.S. forces may have been supplied by Iran, identified as the Chinese-made C-802, which was supplied to Iran and not to Yemen. Other senior military officials, however, say that the missiles could have been models that the Houthi forces already possessed. Yemeni military units under the command of former President Ali Abdullah Saleh that defected to the Houthis had access to the C-801, which was supplied by China to Yemen in 1995, and unsuccessfully launched several at Saudi-led coalition between Oct. and Dec. 2015, according to Tom Cooper in War is Boring.

Analysts who spoke with The Long War Journal believe the Houthi-Saleh forces may have used C-801 or C-802 against the U.S. Navy, and that the C-801 was likely fired at the United Arab Emirates-operated vessel on Oct. 1, based on video footage posted by the Houthis. Iranian and Hezbollah media publicized a drill held by the Houthi-Saleh Yemeni coast on Oct. 4 in reaction to the U.S. Navy dispatch of the Mason, Nitze, and Ponce, warning “the enemies” and “invading Saudi coalition” that any ship approaching Yemen’s waters “without permission” would be targeted.

Although there is no conclusive evidence yet on the weapons system used against U.S. forces, Tehran’s political posturing following the Oct. 8 bombing in Sanaa foreshadowed its support for the missile launches against U.S. forces. On Oct. 9, the IRGC released a statement holding “America, the Zionist regime, and the House of Saud” responsible for the bombing in Sanaa. Top IRGC officials also held the U.S. directly responsible for the attack and for selling weapons to Saudi Arabia. Ali Shamkhani, the secretary of Iran’s Supreme National Security Council, slammed the bombing, and claimed that the attack against the UAE ship was a “legitimate defense” of Yemen’s territory.

Then, on Oct. 13, the IRGC-affiliated agency Tasnim announced that a conventional Iranian Navy group had earlier departed for the Gulf of Aden and the Bab el-Mandeb on Oct. 5 in response to the U.U. dispatch of Navy warships. Iran’s 44th flotilla, comprised of the Alvand frigate and Bushehr support vessel, reportedly intends to “protect shipping lines under attack by pirates” in that area. The deployment, however, was also intended to reinforce Tehran’s commitment to the Houthis, as well as signal Iran’s reach into the Gulf of Aden.

Top Iranian defense officials have denied involvement in attacks against the U.S. and also the presence Iranian advisers on the ground. IRGC Qods Force deputy commander Esmail Gha’ani also denied accusations on Oct. 28 that Iran supplied missiles that struck the UAE-operated vessel – but he did not comment on the attacks against the USS Mason. Gha’ani praised the Houthis for striking the UAE vessel, which he claimed was “cut in half,” making it an attack “unprecedented since World War II.”

“Many aspects about this sinking of this ship has not been revealed yet,” Gha’ani said, “and we are waiting for the Americans to divulge the death of half of their ship crew and other secrets about recent military engagements, but until that time we only suffice with mentioning this truth: in the region called Middle East, Iran is everywhere, though it is not anywhere.”

The second-in-command of Qods Force then boasted on Oct. 28 in a commemoration ceremony for a retired IRGC commander killed in Syria that “the culture of the Islamic Republic” has contributed to the “resistance” in Yemen that is “gaining victory every day.”

Tehran’s calculation in supporting the attacks against the U.S. may have been intended to threaten escalation in order to pressure the U.S. to lean on the Saudis in Yemen. For the past year, the U.S. has consistently signaled that its policy has been to de-escalate the war. The White House has pursued a similar track in Syria, remarking that Iran’s “equities” should be protected in the Levant. These are components of President Barack Obama’s policy in the Middle East for Tehran and Riyadh to “share the neighborhood and institute some sort of cold peace.”

Following the Oct. 8 bombing in Sanaa which appears to violate international law, the White House announced an “immediate review” of its “already significantly reduced support to the Saudi coalition,” calling the bombing the latest in a “troubling series of attacks striking Yemeni civilians.” These signals by the administration continued following the Houthi attacks on U.S. forces, even as the Navy told the Senate Armed Services Committee that Iran supplied the missiles. The White House stressed the limited nature of the response following the retaliation against the Houthi forces, and the desire to not escalate the conflict.

Ultimately, the White House does not want to be in direct conflict with Tehran by escalating against its proxy in Yemen. This has pushed the administration to pressure the Saudis to de-escalate there. It may have been the desired effect of the Islamic Republic.

Although the Houthis are not directly subordinate to Iran as is Lebanese Hezbollah, their cooperation allows Tehran to expand its influence in the Middle East, continue asserting itself as the dominant power, and challenge its arch-rival Saudi Arabia in its own backyard. The latter has been more tempting since the outreaching of the Syrian Civil War in 2012 – an “existential” war for Iran – where Saudi Arabia supports opposition groups and Iran supports Bashar al Assad.

Tony Badran contributed to this report.

Amir Toumaj is a independent analyst and contributor to FDD's Long War Journal.

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