Somewhere in the warm, shallow waters of the Gulf of Oman in late May 2026, Iranian submarines and swarms of fast-attack boats are operating alongside Russian and Chinese warships in a trilateral naval exercise that places three of Washington’s principal strategic rivals inside the same patch of ocean where U.S. carrier strike groups keep standing patrols. The drills, designated Maritime Security Belt 2025 by Tehran, are unfolding near the Strait of Hormuz, the narrow chokepoint through which roughly one-fifth of the world’s traded oil passes every day, according to the U.S. Energy Information Administration.
The exercise is not new. Iran, Russia, and China have staged versions of the Maritime Security Belt series annually for several years, each round growing incrementally in complexity. But the 2025 edition stands out for what Iran’s Islamic Revolutionary Guard Corps Navy brought to the water: submarines and fast boats, the two platform types that form the backbone of Iran’s asymmetric naval strategy and that U.S. Fifth Fleet commanders have long identified as their most persistent tactical headache in the Gulf.
What the three navies are doing
The trilateral composition of the exercise has been confirmed by Associated Press reporting. China, Iran, and Russia are conducting coordinated maneuvers in the Gulf of Oman, continuing a pattern set during the 2024 iteration, which involved a documented flotilla of warships, support vessels, and combat boats from all three countries, including named Russian and Chinese lead ships, according to earlier AP coverage.
The IRGC Navy’s fast boats are small, agile, and often armed with anti-ship cruise missiles. They are designed for swarming tactics: dozens of craft converging on a larger vessel from multiple vectors simultaneously, overwhelming its defenses through sheer volume. Iran has practiced these tactics in the Persian Gulf for more than a decade, and they remain a core concern in U.S. naval planning. The submarines add a layer that is harder to counter. Iran’s undersea fleet includes Russian-built Kilo-class diesel-electric boats, domestically produced Fateh-class coastal submarines, and smaller Ghadir-class midget subs suited to the Gulf’s shallow, acoustically cluttered waters. Which specific hulls joined the 2025 exercise has not been publicly confirmed, but the IRGC Navy’s announcement that submarines were participating is consistent with Iran’s known inventory and its pattern of showcasing undersea assets during high-profile drills.
Russia contributes blue-water surface combatants and long-range strike experience that neither Iran nor China can replicate in these waters on their own. China brings increasingly modern destroyers and frigates, along with a strategic motive: a significant share of Beijing’s crude oil imports transits the Strait of Hormuz, giving the People’s Liberation Army Navy a direct interest in understanding the operating environment. Joint exercises let Russian and Chinese crews train alongside IRGC forces in the confined, high-traffic conditions that define Gulf of Oman operations.
Why the geography matters
The Gulf of Oman is not a remote exercise ground. It sits immediately southeast of the Strait of Hormuz and serves as the gateway between the Persian Gulf and the open Arabian Sea. The U.S. Navy’s Fifth Fleet, headquartered in Bahrain, maintains a near-constant carrier strike group presence in these waters. That means any trilateral formation operating here automatically falls within the detection and engagement range of American naval aviation, Aegis-equipped cruisers and destroyers, and undersea surveillance networks.
The proximity is a geographic fact, not speculation. Over the past two years, the U.S. Navy has cycled carrier strike groups through the region at an elevated tempo, driven in part by Houthi attacks on commercial shipping in the Red Sea and southern Gulf of Aden that began in late 2023 and forced a sustained American naval response. That heightened presence means more American sensors and more American warships sharing the same confined waters with the Maritime Security Belt flotilla, tightening the margin for miscalculation on both sides.
For energy markets and shipping insurers, the signal is hard to miss. Military exercises near the Strait of Hormuz have historically triggered spikes in tanker insurance premiums and brief surges in oil futures. The trilateral nature of this drill amplifies the signal: it is not just Iran posturing alone but three major powers operating in coordinated formation at the world’s most important oil transit point.
What is not yet clear
Several important details remain undisclosed. None of the three governments have published the exercise’s scenario scripts, patrol boundaries, or rules of engagement. It is unknown whether the training includes offensive anti-ship or anti-carrier drills, or whether it is limited to lower-end tasks such as formation sailing, communications interoperability, and search-and-rescue procedures. The gap between what is declared (“maritime security”) and what is practiced behind closed doors is where the real analytical tension sits.
U.S. Central Command has not issued a public statement specifically addressing the submarine and fast-boat deployments in the current drill cycle. That silence is not unusual; the Pentagon typically monitors foreign exercises through classified channels and avoids public commentary unless a direct provocation occurs. But it leaves open the question of how Washington is categorizing the 2025 drills: routine posturing, or a meaningful escalation in trilateral naval cooperation.
There is also no public indication of how closely U.S. forces are shadowing the maneuvers. American P-8 Poseidon maritime patrol aircraft and MQ-4C Triton drones routinely surveil the Gulf of Oman, and it would be unusual for a carrier strike group not to track a foreign submarine operating nearby. But the specifics of any American counter-surveillance effort remain classified.
The pattern that keeps building
Viewed in isolation, any single Maritime Security Belt exercise is a modest event: a few dozen ships, a few days of coordinated sailing, a round of press releases from Tehran, Moscow, and Beijing. Viewed as a series, the picture shifts. Each annual iteration builds institutional muscle memory among the three navies. Communications protocols get smoother. Formation sailing becomes more natural. Officers who trained together one year return the next with a shared operational vocabulary. The cumulative effect is to normalize a trilateral naval presence in waters that, for decades, were dominated by the U.S. Navy and its Gulf Arab partners.
That normalization is the strategic product, more than any single tactical capability demonstrated during the drills. Iran, Russia, and China are signaling that they can operate together in a chokepoint that matters to every oil-importing economy on the planet, and that they intend to keep doing so. For the United States, the challenge is not that one exercise changes the balance of power in the Gulf of Oman. It is that a steady accumulation of exercises, year after year, gradually reshapes expectations about who belongs in those waters and who gets to set the rules.
The presence of IRGC submarines and fast boats in the 2025 edition raises the complexity a notch. Submarines are inherently harder to track than surface ships, and fast boats are inherently harder to defend against in confined waters. Combining both with Russian and Chinese surface combatants gives the trilateral force a wider menu of tactics to rehearse, even if the most sensitive drills never make it into the post-exercise press conference. For now, the exercise continues, the three flags sail together, and the Gulf of Oman remains one of the few places on Earth where American, Iranian, Russian, and Chinese naval power all occupy the same crowded, consequential water.
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*This article was researched with the help of AI, with human editors creating the final content.
