Operation Sentinel
International Maritime Security Construct (IMSC)

On 19 July 2019 US Central Command announced it was developing a multinational maritime effort, Operation Sentinel, to increase surveillance of and security in key waterways in the Middle East to ensure freedom of navigation in light of recent events in the Arabian Gulf region. The goal of Operation Sentinel is to promote maritime stability, ensure safe passage, and de-escalate tensions in international waters throughout the Arabian Gulf, Strait of Hormuz, the Bab el-Mandeb Strait (BAM) and the Gulf of Oman.

This maritime security framework will enable nations to provide escort to their flagged vessels while taking advantage of the cooperation of participating nations for coordination and enhanced maritime domain awareness and surveillance. While the United States has committed to supporting this initiative, contributions and leadership from regional and international partners will be required to succeed. U.S. officials continued to coordinate with allies and partners in Europe, Asia, and the Middle East on the details and capabilities required for Operation Sentinel to enable freedom of navigation in the region and protect vital shipping lanes.

The US invited Germany, France, Britain, Australia, Japan, Norway, Belgium, South Korea and other countries to join its coalition. Following incidents involving commercial vessels near the Strait of Hormuz, Washington invited its allies to take part in a mission in the region to protect freedom of navigation there together. German Foreign Minister Heiko Maas insisted that the US strategy of “maximum pressure” against Iran is an unacceptable scenario for Berlin’s involvement in the region.

Just three hours into his new job, Defense Secretary Dr. Mark T. Esper met with reporters at the Pentagon 24 July 2019 to discuss Iran, China and the proposed defense budget. A top priority: Operation Sentinel, the U.S. Central Command effort to promote maritime stability, ensure safe passage, and de-escalate tensions in international waters throughout the Persian Gulf, the Strait of Hormuz, the Bab el-Mandeb strait and the Gulf of Oman.

The point of Operation Sentinel is to "de-escalate by deterring an escalation — any unnecessary provocation that leads to an unnecessary conflict," Esper said. "[We're] trying to de-escalate and at the same time message [Iran] very clearly, that without precondition, any time, any place, we're willing to meet with them to talk about how we get back on into a negotiation."

The secretary said that for now, the United States would work to make sure U.S.-flagged ships have safe passage over the waterways in the Middle East. "To the degree that circumstances warrant that, if we think a U.S. ship may be under some type of threat — being stopped or being seized — we would want to make sure we have the capacity to make sure that doesn't happen," Esper said. That may include overhead monitoring by unmanned aerial vehicles or could also mean having U.S. warships nearby, he said. "As long as you are in the area, that you can react quick enough to deter the provocation, that's the key," he added.

Esper said he’d be meeting with officials at Centcom and its Navy component to talk more about how Operation Sentinel will work. He emphasized that while de-escalation of conflict is a priority of Operation Sentinel, so too is ensuring safe and free navigation for U.S. ships in the region. "My view is ... we would want to prevent the Iranians seizing or stopping a ship, certainly, for any arbitrary reason whatsoever," he said.

The Europeans were creating their own maritime security force. According to Esper "we said all along is the key thing is here — are two-fold, one is maintaining freedom of navigation in the Strait — of course, the Persian Gulf and the Gulf of Oman — and then secondly is deterring provocative actions from Iran. And so whether we do that as one big group or as subgroups, I think as long as it compliments one another — there will be clearly coordination between us all, CENTCOM will be the coordinating authority.... , most countries who transit the Strait should have an interest in this and want to participate and want to provide some type of forces to ... ensure navigation of the Strait, freedom of the seas, and to deter provocative behavior."

"We are at the beginning stage of developing our maritime security initiative. We will be a part of that but so will be the nations from all across the world. We’ve asked the Brits, the French, the Germans, the Norwegians, the Japanese, the South Koreans, the Australians. I am sure I missed a few", Pompeo said in an interview with Fox News, released late on 25 July 2019. The US Secretary of State insisted that every country that was interested in ensuring security in the Strait of Hormuz needed to participate in the initiative to protect not only its own interests but "fundamental understanding of free and open waterways".

The United States officially proposed to Germany to join its own coalition on shipping security and combat Iranian aggression but was rebuffed by Berlin, which said it would not be part of Washington’s "maximum pressure" campaign against Iran. The United Kingdom called for a European-led mission to secure commercial shipping in the strait, through which a third of the world’s seaborne oil passes after Iran seized a UK-flagged oil tanker, Stena Impero. Berlin did not rule out a naval mission to ensure security in the Strait of Hormuz that would include European countries, the deputy spokeswoman for the German government, Ulrike Demmer, said 31 July 2019. "In principle, the government considers the proposal on a protective naval mission still worth being mentioned, is in contact with European partners, with France and the United Kingdom above all," Demmer told reporters.

On 06 August 2019 Foreign Minister Israel Katz in a closed session of the Knesset Foreign Affairs and Defense Committee said Israel was involved in US-led efforts to provide maritime security in the Strait of Hormuz. Israel was not expected to send ships, but would provide intelligence. Iran on 10 August 2019 said Israel’s possible involvement in a US-led military coalition in the Persian Gulf was a threat to its national security, and vowed to counter Israeli presence in the region. “The announcement made about the possible presence of the al-Quds occupying regime [Israel] in the self-proclaimed military coalition in the Persian Gulf region is a blatant threat to Iran’s national security,” said Iranian Foreign Ministry Spokesman Seyed Abbas Mousavi, according to the semi-official Fars news agency.

Islamic Revolutionary Guard Corps (IRGC) Navy Commander Rear Admiral Alireza Tangsiri warned 11 August 2019 that any illegitimate Israeli presence in the Persian Gulf could spark a confrontation in the region, and that the responsibility for the consequences lies with the United States and the UK. "The United States and the United Kingdom must assume responsibility for the Zionist regime's illegal presence in the Persian Gulf waters. Any presence of the Zionist regime in the Persian Gulf waters is illegal, as it may result in war and confrontation in the region", he told the Lebanese TV channel Al Mayadeen.

The British Royal Navy sent a third warship, the Type 45 destroyer HMS Defender, to the Strait of Hormuz as part of the International Maritime Security Construct to ensure the safe passage of merchant shipping amid growing tensions with Iran. “Wherever the red ensign flies around the world, the UK stands by to protect freedom of navigation whenever is it tested. The men and women of HMS Defender will contribute to the IMSC alongside international partners,” UK Defence Secretary Ben Wallace said 23 august 2019. British warships HMS Kent and HMS Montrose had also been deployed to the region with the latter already completing more than 30 transits through the Strait.

UK Defence Procurement Minister Anne-Marie Trevelyan has stated there is no need to send the HMS Queen Elizabeth to the Strait of Hormuz to defend Britain’s interests in the area in light of last month’s seizure of a British tanker by Iran. “It depends on what you need it for, in the recent [encounter], the Iranian sharp-shooters in the little boats coming out and trying to hijack ships […] the reality is a patrol, a constabulary like Montrose is there to help them through”, Trevelyan said. She added that “those cheeky Iranians in their little fast boats don't mess with” what Trevelyan described as a “very good warship”.

Saudi Arabia said 18 September 2019 it would join a US-led coalition to secure the Middle East's waterways after the attack on its oil fields. The state-run Saudi Press Agency carried a statement quoting an unnamed official saying that the kingdom had joined the International Maritime Security Construct, a mission already joined by Australia, Bahrain and the United Kingdom. Washington formed the coalition after attacks on oil tankers that US officials blame on Iran over Iranian denials, as well as Tehran's seizure of tankers operating in the region.

The United Arab Emirates stated 19 September 2019 that it would take part in a US-led maritime coalition that also includes Australia, Bahrain, Saudi Arabia, and the United Kingdom. Iraq's Foreign Ministry Spokesman Ahmad al-Sahhaf stated that it would not join an international maritime mission to protect commercial shipping in the Strait of Hormuz. The ministry noted the security in the region was the responsibility of the Gulf States.

Trump gave a green light to a "moderate" American military deployment to Saudi Arabia to protect it from possible future attacks coming from Iran. The decision came soon after both the kingdom and Washington accused the Islamic Republic of attacking Saudi Aramco facilities, despite Tehran denying this.

The US redeployed the USS Nitze destroyer to the northeast coast of Saudi Arabia in a bid to "plug the gap" in Saudi Arabia's air defences that was allegedly used in the 14 September raid on its oil facilities. The redeployment comes in line with previous allegations from Washington and Riyadh that the attack came from Iran to the north, rather than from Yemen in the southwest. The USS Nitze has an Aegis launch system on board that is capable of firing both SM-3 missiles to serve as air defence, and Tomahawk missiles as a strike capability. The latter's range would allow the Nitze to deliver strikes anywhere in Iran, if such an order is issued.

In late November 2019 Qatar and Kuwait told the United States that they would join a US-led naval coalition in the Arabian Gulf which was established in response to a series of attacks on oil tankers. “Qatar and Kuwait have already told us they are going to join, so it is just a matter of time,” US Army Colonel John Conklin, chief of staff of the coalition, said. The coalition, which was set up this summer in Bahrain, is known as the International Maritime Security Construct (IMSC).

South Korea will send a navy dispatch to the Strait of Hormuz early next year where it will join a US-led coalition opposing Iranian influence in the critical oil shipping lanes. The Cheonghae anti-piracy unit, patroling the Indian Ocean off the Horn of Africa as part of the multinational Combined Task Force 151, will be ordered to join the coalition. The country's National Security Council decided in mid-December 2019 against deploying a separate unit to join the coalition, but instead to expand the operation of a task force already in the region. According to Korean media, this move would allow Seoul to maintain relations with Tehran while at the same time falling in line with US demands.

Seoul announced 22 January 2020 it will expand the operational area of its anti-piracy Cheonghae Unit "from the Gulf of Aden to the Gulf of Oman and the Arab-Persian Gulf" as part of efforts to help protect vessels passing through the Strait of Hormuz. The 300-strong unit will operate independently from the U.S.-led International Maritime Security Construct in the region, while two liaison officers will be sent to the coalition to coordinate information sharing. Seoul apparently considered both its trade relations with Tehran and Washington's request to contribute to its campaign when making the decision, which comes amid heightened tensions between the U.S. and Iran.

Seoul had informed Tehran of its decision in advance, but a Foreign Ministry official said Iran expressed concerns as Tehran generally opposes foreign troops or ships coming to the region. Iran's Foreign Ministry spokesperson Abbas Mousavi said earlier this week that Tehran cannot accept a decision which is in line with Washington's "adventurist policy," and such a decision doesn't fit the age-old, friendly relations between Seoul and Tehran. Asked about possible negative impacts on Seoul-Tehran relations, a South Korean Foreign Ministry official said the government puts national interest and the safety of South Koreans first, but that it will work closely with Iran to maintain bilateral ties.

The United States welcomed South Korea's decision to expand the scope of its anti-piracy unit’s operations to include the Strait of Hormuz. Though Seoul apparently considered its relationship with Iran in making the move, Tehran has expressed concern. The Pentagon welcomed South Korea's decision to send troops to the Strait of Hormuz to safeguard its citizens and vessels passing through the strategic waterway off Iran's coast. In a commentary on 22 January 2020, Pentagon spokesperson Lt. Col. Dave Eastburn said the U.S. welcomed South Korea's help to ensure freedom of navigation in the Middle East by supporting its coalition in the region, adding the matter is an international problem requiring an international solution. The U.S. State Department also welcomed the move, saying it appreciates Seoul's demonstration of the strength of the South Korea-U.S. alliance and their joint commitment to cooperate on global security concerns.