Iranian Tankers Breach Hormuz Blockade, Highlighting Gaps in US Enforcement

Despite a stringent naval blockade imposed by the US Central Command, two Iranian-linked tankers—Hero II and Hedy, each capable of carrying up to four million barrels of crude—have successfully transited from the Persian Gulf into the Arabian Sea. Their passage has raised critical questions about the effectiveness of the blockade and the evolving tactics employed by Iran’s maritime network.

Strait of Hormuz: Open in Theory, Restricted in Practice

The Strait of Hormuz—a vital artery for global oil and liquefied natural gas—has witnessed severe disruption since late February, following US and Israeli strikes on Tehran and the subsequent collapse of diplomatic efforts.

While Iran briefly declared the strait “open” during a fragile ceasefire on April 17, renewed tensions quickly reversed the situation. By April 18, Tehran signalled a potential closure, accompanied by hostile maritime incidents. Although not formally shut, shipping traffic has dropped sharply, rendering the strait effectively constrained in operational terms.

The blockade, enforced by CENTCOM, specifically targets vessels linked to Iranian ports. Neutral ships bound for other Gulf destinations are permitted passage, provided they are not carrying Iranian-origin cargo. However, US forces retain the authority to intercept and board suspect vessels in international waters.

Since the blockade’s imposition on April 13, US forces have directed at least 28 vessels to turn back. Enforcement has intensified, with high-profile seizures—including the Iranian-flagged Touska and the sanctioned tanker Tifani—demonstrating an expanding operational footprint that extends beyond the immediate Hormuz corridor.

How the Tankers Evaded Detection

According to maritime intelligence reports, the tankers Hero II and Hedy evaded detection by employing a well-established tactic known as “going dark.” This involves disabling Automatic Identification System (AIS) transponders, effectively removing the vessel from conventional tracking networks.

Such practices are a hallmark of Iran’s so-called “shadow fleet,” which routinely circumvents sanctions through covert navigation. Satellite tracking firms observed the vessels crossing blockade zones around April 20, despite heightened surveillance.

A Wider Pattern of Evasion

The two tankers are not isolated cases. Reports indicate that approximately 34 Iran-linked vessels have transited the strait since the blockade began, collectively transporting an estimated nine million barrels of crude oil.

In addition to disabling tracking systems, these vessels employ a range of evasion techniques:

• AIS spoofing: Broadcasting false coordinates to mask actual routes
• Flags of convenience: Registering under foreign flags such as Comoros or Malta
• Coastal navigation: Hugging Iranian territorial waters near Larak Island—often described as a maritime “tollbooth”—to benefit from protective cover

Iran’s Countermeasures at Sea

Iran’s ability to sustain maritime movement is also underpinned by its naval posture. Both the Iranian Navy and the Islamic Revolutionary Guard Corps (IRGC) are reported to provide escort and operational support to tankers navigating contested waters.

Tehran has also established its own controlled transit routes and, at times, has issued warnings or engaged vessels that do not comply with its directives. The narrow geography of the strait—just 21 miles wide at certain points—further complicates enforcement, enabling smaller or agile vessels to manoeuvre through congested channels.

Blockade Effectiveness Under Scrutiny

The continued movement of Iranian oil shipments underscores the limitations of the blockade. While US enforcement has disrupted large volumes of traffic, the persistence of covert exports highlights operational gaps and the resilience of Iran’s logistics network.

Rather than signalling outright failure, the developments point to a contested maritime environment in which control is partial and constantly challenged.

Diplomatic Signals and Strategic Messaging

Amid the maritime standoff, Donald Trump has claimed that Iran is privately seeking to reopen the Strait of Hormuz to mitigate economic losses, despite maintaining a confrontational public stance.

Posting on Truth Social, Trump argued that Tehran’s rhetoric is largely performative, intended to preserve domestic and political credibility.

He further announced an extension of the current ceasefire to allow space for renewed diplomacy. However, the move appears unilateral, with no immediate confirmation from Iran or Israel. Iranian-linked commentary has cast doubt on Washington’s intentions, suggesting the extension may be aimed at preserving strategic leverage while maintaining military pressure.

Outlook

With negotiations stalled and enforcement contested, the Strait of Hormuz remains in a state of strategic ambiguity—neither fully open nor formally closed. The ability of Iranian tankers to bypass restrictions underscores the complexity of maritime control in a high-stakes geopolitical environment.

As tensions persist, the interplay between military enforcement, covert logistics, and fragile diplomacy will continue to shape the trajectory of the crisis and its implications for global energy markets.