Iran File

Iran File: Iran intensifies its escalation around the Strait of Hormuz 

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Iran’s recent attempted seizure of the MV Asphalt Princess and its drone attack against the MV Mercer Street are part of an expansion of Tehran’s view of the Strait of Hormuz as a theater of escalation. Iranian leadership is currently leveraging the strait as part of its ongoing conflict with Israel in other parts of the Middle East rather than using the strait primarily to retaliate against US sanctions, as it previously had. Tehran has shown an intent to cause serious damage to civilian vessels rather than simply disabling or seizing them. Iranian forces have engaged seven ships so far this year, including attacking five tankers currently or formerly owned by Israeli companies. The July 29 drone attack on the MV Mercer Street killed two European crew members, marking the first time that Iran has killed civilians around the strait.

These attacks mark an inflection in the drivers of Iranian escalation in the Persian Gulf and Sea of Oman. Regime forces have harassed and provoked American and British sailors and international shipping around the Strait of Hormuz, over which Tehran claims a degree of sovereignty, for decades. Iran became more aggressive in 2019 and 2020, attacking and seizing tankers as part of its response to the Trump administration’s “maximum pressure” strategy. The regime sought to impose an economic cost on and divide the US and its European and Gulf state partners. However, Iran has directed its escalation around the strait in 2021 primarily at Israel—not the US, Europe, or the Gulf states.

Iranian attacks against commercial traffic have become more frequent in 2021 than in previous years. Iran attacked ships on two occasions and seized vessels on four occasions in 2019. Iran de-escalated slightly in 2020, conducting four tanker seizures and likely placing a naval mine on another without detonating it. Iranian forces have intensified their escalation in 2021, targeting seven vessels thus far—five attacks around the strait and two seizures. Tehran engaged more ships overall in 2019 than it has thus far in 2021, but Iranian forces are targeting commercial traffic in 2021 more often and have shifted to attacking more frequently than seizing.

Iranian forces have begun using more accurate and lethal capabilities in these attacks. The Islamic Revolutionary Guards Corps (IRGC) used primarily naval mines in 2019 and 2020 but involved missiles and drones in 2021. The IRGC conducted as many as two missile attacks on tankers in March and April and one—possibly two—drone attacks in July. The use of missiles and drones reflects the regime’s growing conventional capabilities around the Persian Gulf and Sea of Oman and its willingness to use them against civilian vessels. Iranian leadership has prioritized developing naval missile and drone technologies in recent years and seeks to demonstrate the damage it can inflict in international waterways.

These attacks may mark the start of a longer-term shift in the threat Iran poses around the Persian Gulf and Sea of Oman to the interests of the US and its regional partners. The regime’s recent completion of a pipeline around the Strait of Hormuz may have encouraged Tehran to expand the violence and scale of its attacks in the strait itself. The pipeline—inaugurated on July 22—partly reduces Iran’s dependence on the strait for its own energy exports. It allows the regime to circumvent the strait and export oil from its eastern side, theoretically ensuring international buyers’ access to at least some Iranian oil regardless of a potential maritime conflict disrupting traffic through the strait. Then-President Hassan Rouhani *boasted in June 2020 that the pipeline would guarantee Iranian energy exports even if the strait “was closed.”

Furthermore, Iran seeks to strengthen its conventional military capabilities, particularly following the expiration of the UN arms embargo against it in October 2020. The Defense Intelligence Agency assesses that the regime seeks to field “improved naval mines, faster and more lethal surface platforms, more-advanced [anti-ship cruise missiles], larger and more-sophisticated submarines, and new [anti-ship ballistic missiles].”

These kinds of attacks may become common if the regime has concluded it can conduct a military campaign against civilian vessels without risking serious responses and that it could economically survive a significant disruption of traffic through the Strait of Hormuz. Such a development would pose a serious challenge to the US administration’s stated objective of reducing the American military presence, particularly naval forces, in the region, since Washington cannot cede to Tehran the right to attack and damage civilian shipping in international waterways.