The Hormuz Blockade Conundrum

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by Captain (IN) TSV Ramana (Retd.)*

Background

The United States commenced ‘Operation Epic Fury’ against Iran on 28 February 2026. Subsequently, the US and Iran agreed to a ceasefire, and delegations from both countries held talks in Islamabad from 11 to 12 April 2026, which failed.

On 12 April 2026, US President Donald Trump announced that “U.S. Navy would begin blockading any and all ships trying to enter or leave the Strait of Hormuz” and would “seek and interdict every vessel in international waters that has paid a toll to Iran.”1

However, on the same day, the US CENTCOM issued a press release (dated 12 April 2026), which stated:

“U.S. Central Command (CENTCOM) forces will begin implementing a blockade of all maritime traffic entering and exiting Iranian ports on April 13 at 10 a.m. ET, in accordance with the President’s proclamation. The blockade will be enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman. CENTCOM forces will not impede freedom of navigation for vessels transiting the Strait of Hormuz to and from non-Iranian ports. Additional information will be provided to commercial mariners through a formal notice prior to the start of the blockade. All mariners are advised to monitor Notice to Mariners broadcasts and contact U.S. naval forces on bridge-to-bridge channel 16 when operating in the Gulf of Oman and Strait of Hormuz approaches.”2

Elements of a Blockade

Section II of the ‘San Remo Manual on International Law Applicable to Armed Conflicts at Sea -12 June 1994’ indicates certain qualifiers for a blockade.3 A comparison of the San Remo Manual’s specifications regarding blockade with the US CENTCOM announcement is presented below:

SAN Remo Manual US CENTCOM Announcement
A blockade shall be declared and notified to all belligerents and neutral States Complies via US CENTCOM Release
The declaration shall specify the commencement, duration, location, and extent of the blockade and

the period within which vessels of neutral States may leave the blockaded coastline

Date and time of commencement (April 13, 10 AM ET) is specified but duration is not indicated
Location and extent (The blockade will be enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman) is specified
Period within which vessels of neutral States may leave the blockaded coastline is not indicated in the US CENTCOM press release
A blockade must not bar access to the ports and coasts of neutral States Complies (CENTCOM forces will not impede freedom of navigation for vessels transiting the Strait of Hormuz to and from non-Iranian ports)
A blockade must be applied impartially to the vessels of all States Complies (The blockade will be enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman)

Anomalies Observed

Other than the fact that the US CENTCOM press release does not specify the ‘period within which vessels of neutral States may leave the blockaded coastline’, the other specifications for declaring a blockade as per the San Remo Manual seem to have been met.

The Strait of Hormuz is part of NAVAREA IX. Incidentally, the Hydrographer of Pakistan (HoP) leads both HQ NAVAREA IX and the National Coordinator setup for the purpose of transmission of navigational warnings. As of 14 April 2026, the NAVAREA IX website lists 70 navigational warnings in force.4 However, none pertain to the issue of the blockade of the Strait of Hormuz.

Incidentally, UK Maritime Trade Operations (UKMTO) Advisory 035-26, dated 13 April 2026, addresses this issue. The advisory states that “Neutral vessels currently within Iranian ports have been granted a limited grace period to depart, as will be specified in the NTM (Notice to Mariners).” However, there appears to be no mention of this ‘grace period’ in US CENTCOM’s press release.

Who Will Enforce the Blockade?

Primarily, the US Navy will enforce this blockade. It remains unclear whether warships from other regional or extra-regional countries will participate. According to data from ‘USNI News Fleet and Marine Tracker: April 13, 2026’, the following US naval units are currently deployed or expected to arrive in the region:5

Area US Navy Units Remarks
Arabian Sea 01 x Aircraft Carrier, 08 x destroyers, 01 x Littoral Combat Ship (LCS) & 01 x Amphibious ship Total 11 units
Red Sea 02 x Destroyers Total 02 units
Eastern Mediterranean 01 x Aircraft Carrier, 04 x Destroyers Total 05 units
Heading for the Region as on 14 April 2026 01 x Aircraft Carrier, 03 x Destroyers Total 04 units

There seem to be at least 13 US Navy (USN) units presently in the region that could be involved in the blockade operations. Further, another four may join soon. Thus, at least 17 USN units could eventually be involved.

How a Blockade Should be Enforced?

The Newport Manual on the Law of Naval Warfare (2023) states the following:6

  • A blockade must be effectively maintained by sufficient forces to create a real danger of capture or interdiction for vessels or aircraft attempting to breach it. A blockade is effective if there is a sufficient probability that vessels breaching or attempting to breach the blockade are captured.
  • Assuming that there is a sufficient degree of probability of capture, the distance of the blockading force from the coast is not relevant.
  • There is no rule limiting the type of forces a belligerent State may use to enforce a blockade.
  • So long as vessels or aircraft are in sufficient danger of interception and of being prevented from reaching or leaving the blockaded coast, the blockade will satisfy the “effectiveness” requirement.

Blockade Scenarios

Scenario 1: USN units deploy within the Strait of Hormuz to interdict vessels attempting to enter or leave Iranian ports. This is a very high-risk operation, given Iran’s ability to strike these units and the risk of mines being laid in the area. This scenario seems unlikely at present.

Scenario 2:  USN units deploy off the mouth of the Strait of Hormuz/in the vicinity to monitor the traffic, and to establish the identities of the vessels, flag, port of departure, next port of call, cargo and other relevant details. Thereafter, either the vessels may be permitted to proceed, or they may be directed to stop or turn back. Vessels that do not comply with the directives of USN units may then either be commandeered by boarding or, in the worst case, be fired upon to disable them or be directed to stop and remain in a specified area. This scenario seems more likely.

While scenario 2 may appear theoretically feasible, it also has many complications. Some of these could include: –

  • How should vessels that may disregard the instructions of the blockading USN units be dealt with?
  • Would the USN be willing to fire on these vessels and damage or sink them?
  • Even if vessels comply and stop propulsion, where should they be directed to go?
  • What would be the rules of engagement (RsOE) if vessels of neutral nations and those friendly to the US attempt to either depart from Iranian ports or enter them?

There do not seem to be any easy options for the United States as far as scenario 2 is concerned.

Scenario 3: USN is able to deploy in such a way that all traffic in/out of the Strait of Hormuz ceases. If the situation between the US and Iran escalates, this scenario may become more likely.

What could be the implications of scenario 3 playing out? The disruption in trade to and from the countries of the Strait of Hormuz would be as tabulated below: –7

Country Intracen

Data for Year

Overall Exports

(US$ billion)

Overall Imports

(US$ billion)

Iran 2023 104.4 65.5
Kuwait 2024 75.9 38.1
Qatar 2024 95 35.8
Saudi Arabia 2024 305.3 232
UAE 2024 439.4 444.6
Iraq No data available
Total   1020 816

Scenario 3 could disrupt trade to the tune of US$ 1020 billion in exports and US$ 816 billion in imports.

Scenario 4:  USN imposes a blockade, but certain countries insist on deploying their warships to escort their respective merchant vessels departing Iran/seeking to enter Iran. What would be the reaction of the USN to this? Would the USN be willing to engage in a standoff with these countries or, in the worst case, take hostile action against them? This is a complicated affair. However, this scenario, going by logic, should be unlikely.

Scenarios 2 and 3 seem to be more likely. However, in either case, the progress of the USN’s blockading action and its impact would be subject to many variables that are currently difficult to predict.

In all four scenarios described above, the USN has the option to use its surface ships, onboard helicopters, UAVs, etc., to monitor traffic and enforce the blockade. Further, the tense situation in the region, by itself, may trigger a wariness on the part of concerned nations to transit in/out of the Strait of Hormuz and thereby enabling the United States to achieve its aim of blockading Iran, albeit with collateral damage to other neutral and friendly nations.

How Effective have Blockades been Historically?

The US blockade of Japan in World War II was carried out by warships, submarines and aircraft. There seem to be differing viewpoints on how effective the blockade was. The US blockade of Japan did manage to cut off the supply of certain raw materials, but it was not deemed sufficient to force Japan’s capitulation.8

Indian Navy’s blockade of East Pakistan in 1971 effectively cut off supplies to the Pakistani forces and rendered their continuation in combat moot. This was a classic blockade that proved to be very effective.9

Between October 2023 and October 2025 alone, the Houthis (of Yemen) launched more than 115 complex attacks on commercial and naval shipping in the Red Sea and Indian Ocean; launched missiles and drones at targets in Israel up to 2,600 kilometres from Yemen’s borders; and engaged in a two-month military confrontation with the United States in the Red Sea. This blockade was achieved through asymmetric means and without a navy. The means used were non-naval, yet the blockade was effective.

In December 2025, the United States announced a blockade of all sanctioned oil tankers going into and out of Venezuela and deployed a large military force in the Caribbean near Venezuela. This blockade was effective and caused distress to Venezuela.10

The above examples indicate that varying tactics were used to enforce blockades, with varied results.

Conclusion

The US blockade of vessels transiting in and out of Iranian ports seems to be far more complicated than many earlier blockades, given the strategic situation, Iran’s continued ability to strike USN units and merchant ships of countries it considers inimical to its interests, and the geography of the Strait of Hormuz.

It is debatable whether the US announcement of a blockade is solely intended to inflict economic pain on Iran. It seems more likely that it could be part of a US strategy to turn the tables on Iran by turning its strength (control of the Strait of Hormuz) into a liability and making it difficult for Iran to continue to be seen as the victim of US aggression, especially when it causes severe supply-chain distress for many major countries.

How this US strategy plays out in the coming days cannot be predicted with certainty.

*****

* Captain TSV Ramana (Retd.) is a former Indian Navy Officer and a pioneer of the Indian Navy’s analytical studies vis-à-vis China, with extended tenures in the Directorate of Naval Intelligence at Naval Headquarters, the China Cell at the National Maritime Foundation, at the Maritime Doctrine and Concept Centre (MDCC) as part of the ‘Strategic Maritime Assessment Team (SMAT) – China’ and the Centre for Contemporary China Studies (CCCS). He is a qualified Mandarin interpreter from the School of Foreign Languages at New Delhi. The views expressed are his own.

Endnotes

[1]Mark Nevitt, Just Security, Mined and Blockaded: Iran’s Unlawful Mining and the U.S. Port Blockade, https://www.justsecurity.org/136186/iran-mining-us-blockade/April 13,2026

[2]USCENTCOM, Press Release, U.S. to Blockade Ships Entering or Exiting Iranian Ports, https://www.centcom.mil/MEDIA/PRESS-RELEASES/Press-Release-View/Article/4457255/us-to-blockade-ships-entering-or-exiting-iranian-ports/, April 12,2026

[3]International Institute of Humanitarian Law (IIHL), San Remo Manual on International Law Applicable to Armed Conflicts at Sea -12 June 1994, https://iihl.org/wp-content/uploads/2022/07/SAN-REMO-MANUAL-on-INTERNATIONAL-LAW-APPLICABLE-TO-ARMED-CONFLICTS-AT-SEA-2.pdf

[4]National Hydrographic Office Pakistan, NAVAREA IX Warnings, https://hydrography.paknavy.gov.pk/navarea-ix-warnings/ , 14 April 2026

[5]US Naval Institute, USNI News Fleet and Marine Tracker: April 13, 2026, https://news.usni.org/2026/04/13/usni-news-fleet-and-marine-tracker-april-13-2026, April 13, 2026 3:12 PM – Updated: April 13, 2026 4:32 PM

[6]James Kraska et al, US Naval War College, The Newport Manual on the Law of Naval Warfare (2023), https://digital-commons.usnwc.edu/ils/vol101/iss1/1/, Stockton Center for International Law, Newport, Rhode Island, USA,2023

[7]Author’s analysis of data on exports and imports of Iran, Qatar, Kuwait, Saudi Arabia and UAE from International Trade Centre (INTRACEN), https://www.intracen.org/

[8]Jason Cornish, University of Washington, The Blockade of Japan, https://digital.lib.washington.edu/server/api/core/bitstreams/9cef2810-f517-4fec-a739-6add5eb6cc1a/content,2011

[9]https://digital.lib.washington.edu/server/api/core/bitstreams/9cef2810-f517-4fec-a739-6add5eb6cc1a/content,2011 Indranil Banerjee, The Bangladesh War 1971, Blockade from the Sea, https://www.bharat-rakshak.com/navy/history/1971war/blockade/?utm_source=openai, October 11,2006

[10] United Nations Human Rights, Office of the High Commissioner, UN experts condemn United States blockade and aggression against Venezuela, https://www.ohchr.org/en/press-releases/2025/12/un-experts-condemn-united-states-blockade-and-aggression-against-venezuela, 24 December 2025

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