U.S. Deploys Marines & Warships to Deter Iran

On July 20, 2023, the United States announced the deployment of some 3,000 sailors and Marines with three naval ships to the Middle East in response to Iranian threats to international commercial shipping. The announcement followed the deployment of a guided-missile destroyer, as well as F-35 and F-16 jets, just days earlier.

“In the past two years, Iran has attacked, seized, or attempted seizure of nearly 20 internationally flagged merchant vessels” in the Middle East, U.S. Central Command (CENTCOM) said in a statement. Between May and July 2023, the United States charged that Tehran harassed or seized four commercial ships.

The move reflected escalating tensions between the United States and Iran. Tehran charged that the deployments could raise the risk of conflict. “What do the Persian Gulf, the Gulf of Oman and the Indian Ocean have to do with America? What is your business being here?” asked Brig. Gen. Abolfazl Shekarchi, Armed Forces spokesperson, on August 5. Two days later, Ramazan Sharif, the spokesperson for the Revolutionary Guards, warned that Iran “has reached a level of strength and power that can reciprocate any vicious act by the U.S., such as seizing ships.”

The Islamic Republic has long sought to expel U.S. forces from the Middle East, dating back to its campaign against the Marine deployment in Lebanon between 1982 and 1984. The U.S. military presence in the region “has never created security,” Foreign Ministry Spokesperson Nasser Kanani said on August 7. “Their interests in this region have always compelled them to fuel instability and insecurity.”

The new U.S. deployments included: 

  • Guided-missile destroyer USS Thomas Hudner
  • Amphibious assault ship USS Bataan
  • Transport ship USS Mesa Verde
  • Transport ship USS Carter Hall
  • 26th Marine Expeditionary Unit (some 2,500 Marines)
  • An unspecified number of F-16 fighter jets
  • An unspecified number of advanced F-35 fighter jets

The United States had reportedly also considered deploying Marines on commercial ships. The United States informed the shipping industry that Marines could be available upon request. Members of the 26th Marine Expeditionary Unit began training in 20-person squads in Bahrain in July 2023. The plan had not been approved as of early August 2023.  

Related Material: U.S. Military Deployments Around Iran

CENTCOM “is committed to defending freedom of navigation within our area of responsibility which includes some of the most important waterways in the world,” said Gen. Michael “Erik” Kurilla, the CENTCOM chief, on July 20. More than $1 trillion in goods – including 25 percent of the world’s seaborne crude oil – transits the Strait of Hormuz annually. The strait connects the Persian Gulf and the Gulf of Oman. “It's a critical chokepoint in the maritime world. And we have seen threats by Iran to affect that chokepoint,” John Kirby of the National Security Council said on August 3.

USS Thomas Hudner
The USS Thomas Hudner, a guided-missile destroyer


Past Tensions at Sea

Tensions in the Gulf waters in 2023 were the latest chapter in tense maritime encounters, beginning with the so-called “Tanker War” during the Iran-Iraq conflict between 1980 and 1988. In 1984, Iraq attacked Iranian shipping and refining facilities. Iran reciprocated with attacks on neutral ships, including Kuwaiti tankers. In mid-1987, U.S. naval forces began to reflag and escort Kuwaiti tankers to protect them from Iranian forces as part of Operation Earnest Will. Tensions escalated.  

In October 1987, Iran attacked a Kuwaiti tanker flying a U.S. flag. In response, the United States destroyed two Iranian oil platforms. In April 1988, a U.S. frigate was damaged by an Iranian mine. The United States responded with Operation Praying Mantis, the navy’s largest engagement of surface warships since World War II. Two Iranian oil platforms and two Iranian ships were destroyed. The moves reflected Washington’s willingness to use force to guarantee maritime security.

In subsequent decades, Iranian forces have engaged in sporadic incidents, mainly instigated by the Revolutionary Guards navy, not Iran’s regular navy. The encounters were less violent than during the “Tanker War.” Most involved Iranian harassment of U.S. ships, not live fire. For example, Iranian fastboats approached larger U.S. ships at high speeds, and aircraft flew dangerously close to U.S. vessels.     

Related Material: Timeline of U.S.-Iran Naval Encounters

In 2016, Iranian forces seized two U.S. Navy vessels and held them on Iran’s Farsi Island in the Persian Gulf. Nine men and one woman were aboard the small boats that had drifted off course. The sailors were released after an overnight flurry of diplomatic efforts, including direct engagement between Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif. The two had developed a working relationship during the two years of negotiations that resulted in the historic 2015 nuclear deal between Iran and the world’s six major powers, known as the Joint Comprehensive Plan of Action (JCPOA). 

But U.S.-Iran relations have deteriorated significantly since 2016 for several reasons. In 2018, President Donald Trump withdrew the United States from the Iran nuclear deal and reimposed stringent economic sanctions on the Islamic Republic. In 2019, Iran began to breach its commitments under the accord. In 2021, President Joe Biden launched diplomacy—led by the European Union and also including Russia and China—to revive the JCPOA. But the initiative collapsed in August 2022 when Tehran balked at the final terms. Diplomacy was further complicated by Iran’s support for Russia’s war against Ukraine and its brutal crackdown on protesters. 

The following is a timeline of maritime incidents instigated by Iran during the Biden administration (2021- ).

  • Seizures of commercial vessels: 4
  • Attempted seizures of commercial vessels: 3
  • Attacks or harassment of commercial vessels: 8
  • Hostile or unprofessional encounters with U.S. naval vessels: 9



Feb. 26, 2021: On March 1, Israeli Prime Minister Benjamin Netanyahu blamed Iran for a late-February attack against the Israeli-owned MV Helios Ray in the Gulf of Oman. Iran denied any involvement in the explosion. Israel is “playing the victim to distract attention away from all its destabilizing acts and malign practices across the region,” Ambassador Majid Takht Ravanchi said in a letter to the U.N. Security Council on March 9.

March 25, 2021: The LORI, an Israeli-owned cargo ship that flies a Liberian flag, was struck by a missile in the Arabian Sea. The damage was minimal, and the LORI continued to its final destination in India. A senior Israeli defense official claimed that the IRGC had fired the missile.

April 2, 2021: Three Iranian fast-attack boats and one ship, the Harth 55, approached two U.S. Coast Guard ships, the Monomy and the Wrangell, in international waters in the southern Persian Gulf. The Harth 55 came within 70 yards of the U.S. ships and repeatedly crossed their front bows. “After approximately three hours of the U.S. issuing warnings and conducting defensive maneuvers, the IRGCN vessels maneuvered away from the U.S. ships and opened distance between them,” the U.S. Navy said. In past incidents, U.S. ships were harassed by smaller Iranian vessels.

April 13, 2021: A missile struck the Hyperion Ray, an Israeli-owned and Bahamian-flagged cargo ship, in the Gulf of Oman. The ship was en route from the United Arab Emirates to Kuwait. The ship was reportedly undamaged, according to a spokesperson. Israeli officials reportedly believed Iran was behind the attack. The ship was attacked two days after Israel allegedly sabotaged the Natanz nuclear enrichment facility. Iranian Foreign Minister Javad Zarif had vowed “revenge” on Israel.

April 26, 2021: The USS Firebolt, a patrol ship, fired warning shots after three IRGC fast-attack boats came within 68 yards of it and the USCGC Baranoff, a Coast Guard patrol boat. The incident occurred in international waters of the Persian Gulf. U.S. vessels had not fired a warning shot on Iranian ships since July 2017.

May 10, 2021: The USSCG Maui, a Coast Guard cutter, fired 30 warning shots after 13 IRGC Navy fast boats came within 150 yards of six U.S. military vessels, which were escorting the guided-missile submarine Georgia. Pentagon spokesperson John Kirby said that the number of Iranian boats involved was notably higher than in recent encounters. “This activity is the kind of activity that could lead to somebody getting hurt and could lead to a real miscalculation there in the region, and that doesn’t serve anybody’s interests.” The IRGC denied the U.S. account and said that the warning shots were “provocative.” 

July 3, 2021: The CSAV Tyndall, a formerly Israeli-owned cargo ship that flew the Liberian flag, was struck by either a missile or an unmanned drone in the Indian Ocean while sailing from Jeddah, Saudi Arabia, to the United Arab Emirates. There were no casualties, but the ship suffered minor damage. Israeli security officials believed that Iran was responsible for the attack, Haaretz reported. The ship had previously been owned by Israeli billionaire Eyal Ofer but was sold months earlier, the Times of Israel reported. The vessel's owner at the time of the attack was Polar 5 LTD, a London-based shipping company.

July 29-30, 2021: The Mercer Street—an oil tanker owned by a Japanese company that flew the Liberian flag but was managed by Zodiac Maritime, which is headed by an Israeli shipping magnate—was attacked off the coast of Oman. Israeli officials told The New York Times that multiple Iranian drones were involved in the attack. Two crew members, one British national and one Romanian national, were reportedly killed. “Iran is not just an Israeli problem, but an exporter of terrorism, destruction and instability that are hurting us all,” Israeli Foreign Minister Yair Lapid tweeted. On August 1, U.S., British and Israeli officials charged that Iran was behind the attack. “Iran must end such attacks, and vessels must be allowed to navigate freely in accordance with international law,” said British Foreign Secretary Dominic Raab.

Iran denied involvement while Iranian state media reported that the attack on the tanker was in response to an alleged Israeli attack on al Dabaa airport in Syria. Al Alam News Network cited “informed sources in the region,” but did not specify who attacked the Mercer Street.

Aug. 3, 2021: Iran-backed forces reportedly briefly seized the Panamanian-flagged Asphalt Princess in the Gulf of Oman. Foreign Ministry Spokesperson Saeed Khatibzadeh denied any Iranian involvement. 

Nov. 10, 2021: An Iranian naval helicopter circled the USS Essex in the Gulf of Oman. “There was no impact ultimately to the Essex transit or their operations. But that doesn't mean that this wasn't an unsafe and unprofessional act,” Pentagon Press Secretary John Kirby later said. “Tehran needs to be pressed on why they thought this was a prudent use of their pilots and their aircraft to fly so dangerously close to a U.S. warship.”

May 27, 2022: Iranian naval forces seized two Greek-flagged oil tankers, the Delta Poseidon and the Prudent Warrior, in the Persian Gulf. Iran had vowed to take “punitive action” after Greece seized an Iranian oil tanker, the Pegas, in April at the request of the United States. Washington later confiscated the ship’s oil. 

June 20, 2022: Three IRGC fast-attack boats nearly collided with two U.S. Navy Ships,  the USS Sirocco and the USNS Choctaw County, in the Strait of Hormuz. The boats approached at a “dangerously high speed,” and came within 50 yards of the Choctaw County, which fired a warning flare, according to the U.S. Navy. The incident lasted for about an hour. “We have seen not only in recent days but over the course of many weeks and months that Iran has engaged in maritime activity that is unsafe, that is unprofessional, that puts sailors at risk,” State Department Spokesperson Ned Price said on June 21.

Aug. 29-30, 2022: The Shahid Baziar, an IRGC Navy support ship, seized a U.S. Saildrone Explorer in the international waters of the Persian Gulf. The Iranian ship released the U.S. craft four hours later.

Sept. 1-2, 2022: The Jamaran, an Iranian Navy destroyer, seized two U.S. Saildrone Explorers in international waters of the Red Sea. Iran released the drones 18 hours later. The drones’ cameras were missing, but a U.S. official could not say whether Iran had removed them or they had fallen off.

Nov. 14, 2022: An Iranian-made drone hit a tanker off the coast of Oman. The Pacific Zircon was managed by Eastern Pacific Shipping, a firm controlled by Israeli billionaire Idan Ofer. The company said that the tanker incurred minor damage but that none of the crew members were injured. A day later, the United States confirmed that the drone was an Iranian-made suicide drone. “This unmanned aerial vehicle attack against a civilian vessel in this critical maritime strait demonstrates, once again, the destabilizing nature of Iranian malign activity in the region,” said Gen. Kurilla. An Israeli official said that a Shahed-136 drone, the same type used by Russia in Ukraine, was used in the attack. “We see this as an Iranian provocation in the Gulf – it’s not an attack against Israel – it’s the same thing they usually do in the Gulf, trying to disrupt stability and mainly influence World Cup events.”

Dec. 5, 2022: An IRGC Navy patrol boat attempted to blind two U.S. Navy ships, sea base platform ship USS Lewis B. Puller and guided-missile destroyer USS The Sullivans, using a spotlight at night. The Iranian boat came within 150 yards of the ships in international waters in the Strait of Hormuz. “This dangerous action in international waters is indicative of Iran’s destabilizing activity across the Middle East,” said Col. Joe Buccino, CENTCOM spokesman.

Feb. 10, 2023: The Campo Square—an oil tanker that flew the Liberian flag but was linked to Zodiac Maritime, which is headed by an Israeli shipping magnate—was attacked off the coasts of Oman and India. The reported drone attack caused minor damage to the tanker. There were no reported injuries. A U.S. military official attributed the attack to an Iranian drone. Israeli Prime Minister Netanyahu blamed Tehran. “Last week Iran again attacked an oil tanker in the Gulf [region] and struck at the international freedom of navigation,” he said on February 19.

Iran denied involvement. Israel was “used to leveling allegations against the Islamic Republic of Iran, like its main ally, the United States government,” said Foreign Ministry Spokesperson Nasser Kanaani on February 20.

April 27, 2023: The Iranian navy seized an oil tanker in the Gulf of Oman. The Advantage Sweet–a Marshall Islands-flagged, Turkish-managed, and Chinese-owned ship–was en route to Texas. The Islamic Republic claimed that it had collided with an Iranian ship. “Iran's continued harassment of vessels and interference with navigational rights in regional waters are a threat to maritime security and the global economy,” said the U.S. Navy in a statement. The Iranian move came after reports emerged that the United States had previously seized a tanker carrying Iranian crude oil in April. Iran’s seizure of the Advantage Sweet may have been in retaliation for the U.S. measure, Financial Times reported. 

May 3, 2023: The IRGC seized the Panama-flagged oil tanker Niovi in the Strait of Hormuz. The U.S. Navy released drone footage of the tanker’s capture and said that U.S. ships were in the area at the time of the incident but did not receive a distress call. “Iran’s continued harassment of vessels and interference with navigational rights in regional waters are unwarranted, irresponsible and a present threat to maritime security and the global economy,” the U.S. 5th Fleet said in a statement. The seizure came six days after the Iranian Navy seized a Marshall Islands-flagged ship, the Advantage Sweet. 

June 4, 2023: Three IRGC fast-attack vessels with armed men reportedly harassed the Venture, a Marshall Islands-flagged and Greek-managed ship, in the Strait of Hormuz. The USS McFaul and British HMS Lancaster responded to the ship’s distress call. The United States deployed a P-8 Poseidon reconnaissance aircraft and Britain sent a helicopter to the site. The Iranian ships departed an hour after the U.S. and British response.

July 5, 2023: The Iranian Navy attempted to seize two oil tankers in the Strait of Hormuz. Iran aborted the attempt on the TRF Moss, a Marshall Islands-flagged tanker, after the U.S. 5th Fleet sent the destroyer USS McFaul, a surveillance aircraft, and a drone to the area. A different Iranian ship later attempted to seize the Richmond Voyager, a Bahamian-flagged tanker managed by Chevron. It fired on the tanker and left the area as the U.S. Navy arrived. The following day, Iran claimed that the Richmond Voyager had hit an Iranian ship and injured five people. Tehran said that it had a court order to seize the tanker.


Photo Credit: USS Thomas Hudner via U.S. Navy (Facebook)