Blockade Iran’s Military, Not Just Its Export Revenue

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The U.S. maritime blockade against Iran is not an alternative to war that will compel Tehran to cease hostilities on terms favorable to the United States. But with Iran already challenging the ceasefire, and with its key arsenals still posing serious threats, a blockade can help bring about the best possible culmination of the U.S.-led military campaign.

This requires President Trump to expand the blockade’s explicit scope beyond its current narrow focus on Iran’s exports. As important as it is to deny revenues for the regime’s reconstitution, it is equally important to uphold global UN Security Council (UNSC) sanctions by interdicting Iran’s military resupplies from China and others. Ideally, the blockade also would support vital U.S. national security interests in restoring freedom of navigation in the Strait of Hormuz and Persian Gulf, though this entails greater risk by moving the blockade closer in and contesting Iranian naval forces. Failing to do so, and letting Tehran profit from holding these seas, will undermine Trump’s stated purpose for the blockade and wartime objectives. It also will pose far more enduring security and economic challenges than the current disruption in this crucial chokepoint.

To What Ends?

On April 13, U.S. Central Command (CENTCOM) implemented a maritime blockade “against vessels of all nations entering or departing Iranian ports and coastal areas.” In announcing the blockade the day prior, President Trump said the U.S. Navy also would intercept ships paying Iranian tolls to transit the Strait of Hormuz. As of April 14, at least 16 U.S. warships, as well U.S. military aircraft and other forces, were in place in and around regional waters to enforce the blockade, with additional warships on the way.

Coming in the wake of talks that failed to reach an agreement on ending the war, Trump’s declaration indicates the intent, by denying revenues to Tehran, to compel concessions over its nuclear program and its own efforts to control passage through the Strait. But Iran appears unready to soften its diplomatic stance in any meaningful way, precisely because it believes it still holds the better cards on these issues. While certainly diminished, its nuclear, missile, drone, attack boat, and naval mine arsenals are by no means eliminated. Its threats to freedom of navigation offer much-needed toll revenues, and act as pain points on the United States and its regional and global partners. Believing they withstood their worst enemies’ best shot at overthrowing them, the regime’s new leaders could well view compromise and concessions as potentially existential threats.

Even if it does not induce negotiating concessions, an effective blockade of Iranian ports and coastal areas could help advance several important U.S. wartime objectives:

1. Denying revenue-generating exports: CENTCOM officials estimate that 90 percent of Iran’s economy depends on seaborne trade, with oil exports now accounting for nearly all of the regime’s revenues. Iran’s energy exports, most of which go to China, actually rose in March as the Trump administration waived relevant U.S. sanctions and demand for these products rose as the rest of the region’s energy exports fell precipitously. Blockading these exports could starve the regime of vital funds needed to reconstitute its damaged military capabilities. Based on initial statements from American officials, this is the primary—and possibly sole—objective of the blockade, at least thus far.
2. Denying military-related imports: Iran has demonstrated real ability to revamp its nuclear and military infrastructure following prior conflicts in October 2024 and June 2025, leveraging Chinese assistance to expand its missile production capacity. Beijing reportedly now is considering replenishing Iran’s air defenses, and Chinese firms regularly provide key technologies and materials for Iran’s defense industry. As part of enforcing globally binding UN Security Council (UNSC) sanctions, a blockade could intercept Chinese, Russia, North Korean, and others’ resupply of critical raw materials, components, technologies, and weapons systems to assist Iran’s military rebuild.
3. Denying Iranian toll revenues and threats to freedom of navigation: even with Iran’s conventional fleet largely sunk, the Islamic Revolutionary Guard Corps Navy (IRGCN) can still function to some extent as an “anti-navy” using fast-attack craft, naval mines, coastal defenses, unmanned surface vehicles (USV), and marine infantry to deter or attack U.S. Navy and commercial vessel operations in the Gulf of Oman, Strait of Hormuz, and Persian Gulf. These same capabilities underpin Iran’s ability to extract tolls from vessels seeking safe transit via Hormuz—extortion that could compensate for 15-20 percent of its own energy export revenues that are lost to the U.S. blockade. Though Trump’s and CENTCOM’s statements did not specify the type(s) of vessels subject to the blockade, other than their origin and destination, the U.S. Navy legal handbook’s definition of the goal of a blockade—“denial and degradation of an enemy’s capability, with the ultimate end-state being defeat of the enemy”—suggests it could include subverting IRGCN operations to control and disrupt passage through the Strait.

The first two objectives could be pursued by commanding sea lanes, centered in the Arabian Sea and Gulf of Oman, that connect Iran to its economic and military partners. In addition to operating beyond range of Iran’s anti-ship missiles and drones, this takes advantage of geography, as seaborne trade to and from Iran naturally funnels through the Gulf of Oman and into Hormuz and the Persian Gulf. This distant form of blockade could resemble recent U.S. interdiction efforts on the open seas against certain sanctioned tankers traveling to or from Venezuela, and last November’s U.S. seaborne raid in the Indian Ocean that seized military-related cargo on a ship bound from China to Iran. Historical operational successes that roughly mirror this second objective—denying or limiting military resupplies to Iran—can be found in the U.S.-led 1965-72 maritime blockade of North Vietnamese military resupplies to communist forces in South Vietnam, and the North Atlantic Treaty Organization’s (NATO) 1992-96 maritime blockade to uphold a UN arms embargo against Yugoslavia.

A distant blockade could be “open” in the sense that it does not necessarily intercept every single ship that meets proper criteria. Similar to how perceived risks of Iranian attack suffices to prevent many ships from transiting the Strait, the prohibitive costs for shippers of losing valuable vessels and cargo to seizure could outweigh even objectively low odds of actually being stopped in an open blockade as they move to or from Iranian ports. Reportedly six merchant vessels, at least five of which were carrying oil, returned to Iranian ports as per U.S. warnings in the first 24 hours. As a tradeoff for reduced strains on U.S. forces, however, an open blockade raises the chance that certain ships could slip through.

Interfering directly with Iran’s naval operations would entail more of a close-in blockade than is reflected in current U.S. deployments or statements. This would target IRGCN movements in the Strait, both adjoining gulfs, Iranian coastal waters, and Iranian ports themselves. Compared to blockading oil tankers and cargo ships in the open sea, this option involves the greater operational demands and risks of naval and air operations to transit the Strait of Hormuz at will and reestablish military presence inside the Persian Gulf—all in the teeth of potential IRGCN counterattacks. Yet, in a potential precursor of this approach, the day before President Trump announced the blockade, U.S. Navy warships transited the Strait and entered the Persian Gulf for the first time since the start of the war before returning to the Gulf of Oman. As rough historical analogies, Japan’s 1904-05 naval blockade of Port Arthur, and India’s 1971 naval blockade of Karachi, bottled up Russian and Pakistani warships, respectively, and helped prevent them from conducting operations.

The Next Phase of Conflict, Not the Alternative

By itself, a blockade will neither collapse the already-shaky ceasefire nor end the war on favorable terms for the United States. Even before the blockade’s announcement, Tehran aimed to erode U.S. resolve and leverage by continuing to toll Hormuz shipping, threaten freedom of navigation, and conduct drone attacks on Arab Gulf countries. Iranian statements since then essentially describe what it already is doing, with its Armed Forces Central Headquarters warning “if Iran’s ports are threatened, NO PORT in the region will be safe,” and the IRGC saying the blockade is “piracy” that could end the ceasefire and trigger retaliation across the region.

Absent an unexpectedly marked, swift, and concrete shift in Tehran’s diplomatic position, the Trump administration must decide how to foster an acceptable postwar outcome in light of its stated goals to dramatically diminish Iran’s nuclear, missile, naval, and other military capabilities. Talks let Tehran play for time and position, creating the most auspicious conditions either for an accord that falls well short of U.S. redlines or, failing that, a resumption of major hostilities.

A blockade seems unlikely to alter the prospects of negotiations, meaning it will do little to change the basic fact that America’s strategic choice is between a bad deal and the best possible culmination of military operations. But a blockade can support the latter by denying Iran vital funds and materiel to reconstitute its most threatening arsenals, and by degrading its remaining ability to hold at risk commercial vessels in the Strait and adjoining waterways. Accordingly, it should be directed in a broader effort to maximize the attrition to Iran’s arsenals before the conflict ends one way or another. This would facilitate the conditions for the regime’s eventual collapse, before it can rebuild militarily in any meaningful way. It also will reduce the barriers to action for future U.S. administrations that may be less likely to resort to force.

To this end, the U.S. blockade must, at minimum, enforce UNSC sanctions by targeting inbound ships that might resupply Iran’s military in the same way it intends to target outbound ships laden with revenue-generating Iranian exports. Current U.S. force posture in the Arabian Sea and Gulf of Oman can support this objective, and clear U.S. statements to this effect can help deter any military resupply ships from attempting to reach Iran.

Ideally, the blockade also will form part of a larger plan to reassert U.S. military dominance in Hormuz and the Persian Gulf. More than two full days into the blockade, there have been no statements or close-in deployments indicating any such intent. Demonstrating America’s ability to hold the sea, preventing Iranian minelaying, and projecting air and naval power are prerequisites for restoring freedom of navigation and, if need be, escorting commercial vessels. Failing to do so, and letting Tehran think it holds this maritime chokepoint, poses far more enduring challenges than the current shutdown.

And just as a blockade can better degrade Iran’s capabilities than affect its defiant intentions, the president’s recurrent coercive threats to strike desalination and power plants should be ditched in favor of preparations to degrade further the regime’s military capabilities. Iran has shown its ability and willingness to retaliate in kind throughout the war, and it could inflict potentially catastrophic damage, with outsized strategic effects, by attacking similar critical infrastructure in Arab countries. Tehran’s edge in such “countervalue” escalation should reinforce the merits for the United States of a counterforce approach to neutralize the regime’s military assets that enable it to continue threatening these and other high-value targets like the Strait, and to continue exacting tolls at Hormuz. A robust blockade will be a crucial, but by itself insufficient, element of this operational concept.

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