On Monday, April 13th, the United States announced that the US Navy would block Iranian ships entering or exiting the Strait of Hormuz. The announcement came after the first-round of negotiations to formally end the conflict concluded in Islamabad, Pakistan without agreement. 

The American announcement sparked confusion about scope and enforcement and how the US Navy would interdict ships that enter or leave the narrow Strait of Hormuz, which Iran has effectively blockaded since the start of the US-Iranian conflict. 

The Foreign Policy Research Institute (FPRI) gathered three naval experts to shed light on the unfolding situation and what it may mean.

Emma Salisbury, Senior Fellow

The precise naval assets committed to enforcing the blockade remain unknown, but the Strait of Hormuz represents one of the most challenging theaters imaginable for maritime operations. Barely 21 miles across at its narrowest, the waterway is busy and flanked by Iranian territory, factors that combine to make blockade enforcement a formidable undertaking.

Executing such an operation would demand serious capabilities. Arleigh Burke-class destroyers would likely form the backbone of the US Navy surface presence, projecting visible force while managing air defense and the physical interception of vessels attempting to breach any exclusion zone.

Carrier airwings—built around F/A-18 Super Hornets and supported by E-2D Hawkeyes providing airborne early warning coverage—would need to maintain a continuous tempo of operations to neutralize Iranian missiles and drones launched from the mainland. Land-based Air Force platforms would need to supplement these efforts considerably.

Underpinning all of this would be the need for persistent intelligence, surveillance, and reconnaissance (ISR). P-8 Poseidon maritime patrol aircraft and an array of unmanned systems would need to maintain coverage of the strait’s shipping lanes, necessary to distinguish lawful transit from blockade-running, and to identify emerging threats from the Iranians.

It remains to be seen how long this blockade will last and what the Iranian response will be, but we can at least add “blockading a blockade” to the annals of American naval operational experience.

Michael Petersen, Senior Fellow

The US blockade of the Strait of Hormuz does not appear to be a traditional close blockade, with warships lying in wait, controlling waterspace, and pouncing on blockade runners. Instead, what is likely—and appears to be unfolding—is a “distant (or semi-distant)” blockade of vessels that have, in President Donald Trump’s words, “paid a toll to Iran.” This approach has advantages and disadvantages over the more traditional alternative. 

While a close blockade can secure tight control over a limited area, it carries enhanced tactical risk. A distant blockade can secure limited control over an unlimited area with less tactical risk. The US Navy only has only partial advantage over Iran’s “anti-navy” of fast attack craft, mines, and coastal cruise missiles, so a distant blockade lowers risk to the force. It also allows US warships outside US Central Command (CENTCOM) to interdict ships worldwide, lowering pressure on other combatant commands to send ships there. 

This approach requires significant assistance from allies and partners to be fully successful. Allies and partners must be willing to impound ships, even those waylaid by the US Navy. Assistance with sustained, global, maritime domain awareness is necessary to provide persistent tracking of suspect ships and minimize the benefits of “flag hopping” and “dark fleet” operations. Little of this appears forthcoming.

Frank Hoffman, Senior Fellow

The establishment of a blockade of the Strait of Hormuz seems to be aimed at negating what Iran believes to be its strongest source of economic leverage. Rather than accept Iran’s “asymmetric advantage” in geography President Trump is going to seize control with his own asymmetric naval strength. Instead of permitting the Iranians to determine who and what passes through its waters and the international channel, Trump has said he will block shipping from entering or exiting the Persian Gulf. Furthermore, he supposedly ordered the US Navy with the legally questionable mission of hauling down ships that have paid a toll and already transited out of the Gulf. 

By shutting down international shipping from using the strait, Trump would deny Tehran a major supply of revenue. This would impinge on its ability to continue financing its government and military operation, but also exacerbate rising energy prices and financial markets around the world. The People’s Republic of China (PRC) is unlikely to appreciate PRC-bound loads on PRC-flagged vessels being blocked from bringing crude into its ports. Hopefully, the White House has war-gamed likely reactions including another delay in the Xi/Trump summit or a not so subtle squeeze in rare earth metals.

It is not clear exactly how the Pentagon is implementing the order. It appears to have assessed and narrowed the mission as a blockade of Iranian ports rather than the Strait of Hormuz itself. This framing appears better suited to satisfy international law, as blockades are an act of war.

Enforceability of blockades are not beyond the capability of the US Navy given the narrow character of the strait, but it could prove to be both ship and manpower intensive if the CENTCOM task force has to physically blockade ports inside the Gulf and in the Gulf of Oman. It would take several destroyers on station to enforce the blockade, and they could be subjected to missile or small boat attacks. Air cover or integrated missile defense resources would be at a premium. It may be necessary to employ Sailors and Marines to board tankers and major ships to inspect cargo and manifests. The existing Marine contingents in the area are capable of conducting such helicopter-borne Vertical Boarding Search and Seizure operations. Iran may seek to deflect such tactics by deploying military assets (ground troops and drones) to “ride shotgun” on nationally-flagged ships and risk a naval escalation. Iran may attempt to swarm the blockading ships with fast small boats with anti-ship missiles. The enthusiasm behind such attacks is likely to dissipate quickly after a few sorties meet the Navy’s strike aircraft or the Marine’s deadly attack helicopters on the Amphibious Ready Group.

Image: A vessel at the Strait of Hormuz, off the coast of Oman’s Musandam province, April 12, 2026. (REUTERS/File Photo)