Strait of Hormuz: Why Iran’s Small Speed Boats Are Difficult to Defend Against

 

Iran’s military declared on April 18 that the Strait of Hormuz had returned to closed status, reversing a brief opening announced the day before after Trump confirmed the U.S. naval blockade of Iranian ports would remain in place. The UK Maritime Trade Operations center confirmed that IRGC gunboats opened fire on a tanker transiting the strait on April 19, describing the vessel and crew as safe.

At least two additional vessels came under fire during the same period. Iran’s parliamentary speaker and chief negotiator Mohammad Bagher Ghalibaf stated on Iranian state television: “It is impossible for others to pass through the Strait of Hormuz while we cannot.”

Understanding the current threat requires distinguishing between two separate Iranian naval forces. Iran’s conventional navy, the Islamic Republic of Iran Navy, known as IRIN,  has sustained severe losses and is assessed by U.S. officials as largely combat-ineffective.

The force actually controlling the strait is the IRGC Navy, a separate organization with different doctrine, equipment, and command structure. CENTCOM reported more than 155 Iranian vessels damaged or destroyed, but U.S. public statements did not consistently specify which navy those losses came from. The Soufan Center assessed that the strait closure was accomplished primarily by IRGC fast-attack craft using direct fire against tankers, without requiring missiles or drones, and that this represented Iran’s most effective strategic tool, causing global shipping companies to anchor vessels and refuse transit rather than risk attack.

The Wall Street Journal, cited by the Times of Israel and Roya News, reported that more than 60 percent of IRGC fast-attack boats remain intact. Former Pentagon official David de Roches, quoted in that reporting, stated that smaller vessels are significantly harder to detect using satellite surveillance than conventional warships. Jane’s defense reference, one of the most authoritative open-source defense databases, identifies the IRGC Navy as the most prominent practitioner of small boat swarm tactics combining speed, mass, coordinated maneuver, and low radar signature, though this characterization was accessed through secondary sourcing rather than directly from Jane’s.

That low radar signature is structural. Fiberglass-hulled small boats operating at sea level return a radar cross-section comparable to wave clutter, making them difficult to distinguish from the sea surface in waters where hundreds of legitimate small craft operate daily.

The engagement window problem compounds the detection challenge. By the time a boat emerges from a concealed coastal position, closes on a vessel, and fires, the time available for a defensive response is extremely short.

CENTCOM has acknowledged both threat categories as distinct and persistent. In response, it has deployed A-10 Thunderbolt II jets specifically against fast-attack watercraft and AH-64 Apache gunships specifically against one-way attack drones.

The pre-war size of the IRGC small boat fleet is genuinely unknown and the figures in circulation vary dramatically. The one verifiable Western data point is a 2007 U.S. Office of Naval Intelligence estimate of 1,000 IRGC speedboats, described at the time as a growing fleet. Figures ranging from 3,000 to 5,000 vessels attributed to 2020 reporting appear only in Wikipedia’s IRGC Navy article without a traceable citation and may be the result of iRGC propaganda efforts.

Similarly, figures of 33,000 Basij Navy boats and 55,000 Basij sailors exist only in that same Wikipedia article with no sourcing. A 2024 research note by France’s Foundation for Strategic Research, drawing on 2019 U.S. Navy intelligence data, listed the IRGC fleet as consisting primarily of MK13, Peykaap I/II/III, and Ashoora coastal patrol boats without providing a total vessel count, and stated explicitly that the exact number of vessels is not publicly known.

One Iranian news outlet claimed at least 1,500 speedboats of specific named classes in 2022, but Iranian open-source figures cannot be independently verified. A Basij parade in November 2020 reportedly featured around 1,000 boats, but that figure came from Al Manar TV, a Hezbollah-affiliated outlet. Farzin Nadimi, among the most cited Western specialists on the IRGC Navy, declined to provide a specific number.

The reliable working range from credible Western sources is therefore several hundred to several thousand fast boats, with the pre-war baseline genuinely unknown. Furthermore, there is no clearly defined, quantified, and verified number for the boats destroyed since the beginning of the conflict.

Some media have claimed that roughly half of Iran’s naval capabilities remain intact. However, the baseline was never defined. If the IRGC small-boat pool numbered in the thousands before the conflict, CENTCOM claims of destroying 155 total Iranian vessels across both navies would represent only a small fraction of that pool, not half.

If the “half” claim refers only to formally classified IRGC warships, which numbered roughly 50 named craft, including 10 Houdong missile boats, 25 Peykaap II missile boats, five C-14 boats, and ten MK13 boats as of June 2025 reporting, then CENTCOM strikes may have destroyed close to all of them. Media framing appears to conflate these two distinct categories.

The practical conclusion is that Iran’s formal naval warfighting capacity is largely gone, while its capacity to deploy armed speedboats against tankers, drawn from a pool of uncertain but substantial size, has not been meaningfully degraded.

On missiles and drones, DIA director Lt. Gen. James Adams told Congress in a written statement submitted to the House Armed Services Committee that Iran retains thousands of missiles and one-way attack drones, that the remaining systems can threaten U.S. and partner forces throughout the region despite degradations, and that Iran poses a persistent threat to freedom of navigation in the Persian Gulf, Strait of Hormuz, and Gulf of Oman.

Approximately half of Iran’s roughly 470 pre-war ballistic missile launchers are assessed as intact, with around 200 destroyed and 80 rendered non-operational. Underground tunnel and cave networks built over decades have been the primary reason launchers have survived. Mobile platforms that fire and relocate have compounded targeting, a problem U.S. forces encountered similarly with Houthi forces in Yemen.

The Shahed-136 one-way attack drone presents a separate problem. It is cheap, produced in simple factories, and requires no complex launcher. Despite a slow airspeed that makes it theoretically vulnerable to helicopter interception, many have penetrated U.S. and Gulf air defense systems throughout the conflict. As one analyst cited by Al Jazeera put it, maintaining a credible threat matters more than launch volume.

IRGC Aerospace Force commander Brig. Gen. Seyed Majid Mousavi stated on Iranian state media during the ceasefire that Iran had repaired missiles and drone launchers and that the speed of replenishment exceeded the pre-war rate. Iranian state television broadcast footage of missiles and drones in warehouses alongside mobile launch activity. These are Iranian government claims and carry the caveat that Tehran has incentives to overstate recovery.

On mines, the evidence is contested and the public record is contradictory. At a mid-March Pentagon briefing, Joint Chiefs Chairman Gen. Dan Caine stated that missiles, not mines, were the primary threat to merchant shipping, and that the U.S. had seen no mine-laying activity by unmanned surface vessels in the Gulf. Defense Secretary Hegseth stated there was no clear evidence Iran was mining the strait, and that no ships had struck mines.

CNN reported in early March, citing unnamed intelligence sources, that Iran had begun laying a few dozen mines. The New York Times reported, citing senior U.S. officials, that the IRGC mined the strait chaotically using small boats in the immediate aftermath of the February 28 strikes, without a clear command chain or recorded coordinates, meaning Iran subsequently could not locate all mines it had placed and lacked the capacity to remove them. The IRGC’s navigation notice to mariners stated there was a “likelihood of the presence of various types of anti-ship mines in the main traffic zone.” U.S. officials later said fewer than ten mines had been laid.

Mine-clearing operations began April 11 with USS Frank E. Petersen and USS Michael Murphy transiting the strait. USNI News, which tracked the conflict’s maritime incidents throughout, reported that there had been no confirmed instance of any vessel striking a mine, with the 29 vessels hit by Iranian projectiles all attributed to missiles, drones, or direct gunfire.

Iran’s choice to use projectiles rather than rely primarily on mines reflects a strategic calculation noted by analysts at the American Enterprise Institute’s Critical Threats Project: projectiles allow Tehran to selectively permit or deny passage, whereas indiscriminate mining would endanger Iranian-approved ships and Chinese vessels, undermining the political and economic leverage the strait closure is designed to create.

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