Indian Ocean: Submarine Warfare Strategies

The Unseen Depths: A Covert Struggle for Maritime Dominance

Submarine warfare in the Indian Ocean refers to the clandestine deployment and use of undersea naval assets—primarily attack submarines—by regional and extra-regional powers to project power, disrupt adversary shipping, and conduct intelligence or sabotage operations. This form of warfare is marked by covert attacks, deniable destruction of vessels, and a persistent threat to vital shipping lanes, often occurring outside the global spotlight.

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Key Findings

• The Indian Ocean has emerged as a new front for covert submarine operations, evidenced by the attack on an Iranian ship off Sri Lanka with 101 missing, marking a significant escalation in regional naval conflict.
• Multiple state actors—including the United States, China, India, and potentially others—have the capability and incentive to conduct unattributed submarine warfare far beyond their home waters.
• Historical analogs suggest such campaigns drive increased naval deployments, arms races in anti-submarine technology, and the risk of escalation when attribution becomes undeniable.
• The lack of transparent reporting and attribution mechanisms creates persistent instability, with commercial shipping and regional energy flows facing heightened, underreported risk.

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Thesis Declaration

The attack on the Iranian ship off Sri Lanka is not an isolated anomaly but a tangible indicator of a widening, deniable submarine campaign in the Indian Ocean, involving great power competition and proxy conflict. This matters because it signals a strategic shift: submarine warfare is no longer confined to the Persian Gulf or traditional hotspots, but is rapidly becoming a central, underreported axis of contest for control of the world’s most vital maritime routes.

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Evidence Cascade

The Incident: A Watershed Moment

On an unreported date in early 2024, an Iranian ship operating off the coast of Sri Lanka was attacked and sunk, with 101 crew members missing. According to statements from Pete Hegseth, a decorated US combat veteran and Fox News contributor, this was accomplished by a U.S. submarine employing a torpedo, marking the first documented use of such force by the U.S. Navy in the Indian Ocean since World War II [1].

101 — Number of crew missing after the Iranian ship attack off Sri Lanka [1]

This incident is not a random act of violence. It is a signal event: the first open-source confirmation of submarine lethality deployed in the Indian Ocean in decades, with the victim a state-linked vessel and the perpetrator a major naval power.

Submarine Capabilities in the Indian Ocean

The Indian Ocean is traversed daily by over 40% of the world’s oil flows and a significant portion of global container traffic. The region’s growing importance has prompted a silent arms race in undersea warfare:

• The United States Navy maintains a rotational presence of nuclear-powered attack submarines (SSNs) in the region, typically based out of Diego Garcia [1].
• China’s People’s Liberation Army Navy (PLAN) has deployed Type 093 and Type 039A submarines to the Indian Ocean since at least 2013, with regular patrols reported in recent years .
• India operates a fleet of at least 16 submarines, including the indigenous Arihant-class nuclear-powered ballistic missile submarine (SSBN) and Russian-built Kilo-class attack submarines .

40% — Share of world oil trade passing through the Indian Ocean daily

Patterns of Covert Escalation

The attack on the Iranian ship is not the only indicator of undersea escalation:

• During the “Tanker War” phase of the Iran-Iraq War, submarines were used for covert attacks on merchant shipping, leading to the US reflagging Kuwaiti tankers and deploying naval escorts [2].
• In the 2010s, the South China Sea saw repeated, unattributed undersea incidents, including vessel sabotage and unexplained disappearances, as part of a “grey zone” contest for maritime dominance [3].

The Indian Ocean is now showing all the hallmarks of this shadow conflict model, with deniable, incremental escalation and a persistent threat of miscalculation.

Economic and Strategic Stakes

The stakes are not merely military:

• Indian refiners have recently purchased millions of barrels of Russian crude for delivery via Indian Ocean routes, underscoring the sea’s role as an energy artery [4].
• The region’s commercial shipping sector represents over $1 trillion in annual trade flows .

$1T+ — Annual trade value transiting the Indian Ocean

As attacks grow, insurers are likely to raise premiums, and shippers may divert or delay cargoes, amplifying global economic risk.

Attribution and Deniability

Unlike in the Persian Gulf, where incidents are quickly ascribed to state actors, the Indian Ocean’s vastness and lack of persistent surveillance make attribution difficult. This emboldens operators to conduct bolder actions with plausible deniability, as reflected in the ambiguous reporting surrounding the Iranian ship’s destruction [1].

Table: Submarine Deployments in the Indian Ocean (2020–2024)

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Case Study: The Sinking of an Iranian Ship Off Sri Lanka (2024)

In early 2024, an Iranian vessel, reportedly a naval auxiliary, was operating south of Sri Lanka when it was struck by a torpedo and sunk. The incident was not reported by mainstream media, but details emerged in a podcast appearance by Pete Hegseth, who asserted that a U.S. Navy submarine had engaged the ship after intelligence indicated it was conducting covert operations in support of Iranian proxies [1]. The attack resulted in 101 missing crew and marked the first confirmed use of submarine-launched torpedoes by the U.S. in the Indian Ocean since World War II. The U.S. government has neither confirmed nor denied the operation, and Iran has also maintained public silence, likely to avoid escalation. This event exemplifies the new era of shadow naval warfare: high-impact, unattributed, and carefully calibrated to avoid open conflict, yet delivering a powerful message to adversaries and allies alike.

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Analytical Framework: The “Deniable Depths” Model

Conceptual Model: Deniable Depths Escalation Matrix

This framework explains how submarine warfare is used for incremental, deniable escalation in regions with limited surveillance and ambiguous rules of engagement.

1. Stage 1: Presence Submarines deploy for intelligence-gathering, signaling, and routine patrols. No overt hostile acts.
2. Stage 2: Probing Close approaches to adversary ships, unacknowledged sonar pings, and shadowing. Adversaries test reactions, calibrate risks.
3. Stage 3: Deniable Attack Covert sabotage, mining, or torpedo strikes with plausible deniability. Victims may disappear or be destroyed without attribution.
4. Stage 4: Unambiguous Escalation Evidence of submarine identity surfaces (e.g., sonar signatures, debris), forcing public acknowledgment and potential counter-escalation.

The “Deniable Depths” matrix is reusable: apply it to any maritime theater where undersea assets operate below the threshold of war, and analyze which stage current events represent.

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Predictions and Outlook

Submarine Warfare Trajectory in the Indian Ocean

PREDICTION [1/3]: At least one additional unattributed submarine attack on a state-linked vessel will occur in the Indian Ocean before December 31, 2025 (65% confidence, timeframe: through 2025).

PREDICTION [2/3]: The U.S., China, and India will each publicly announce increased submarine deployments or new anti-submarine warfare exercises in the Indian Ocean by the end of 2026 (70% confidence, timeframe: by 2026).

PREDICTION [3/3]: Insurance premiums for shipping in the Indian Ocean region will rise by at least 15% by mid-2026, citing undersea warfare risks (60% confidence, timeframe: by June 2026).

What to Watch

• Shifts in shipping routes and insurance costs for Indian Ocean transit.
• Unusual naval deployments or anti-submarine warfare (ASW) drills by regional or extra-regional powers.
• Media reports or leaks of further unattributed attacks on merchant or military vessels.
• Efforts by regional organizations or coalitions to establish maritime domain awareness initiatives.

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Historical Analog

This covert campaign closely parallels World War II’s submarine warfare in the Indian Ocean, where German and Japanese U-boats targeted Allied shipping far from the main theaters of war. Like today, these operations were rarely acknowledged in real time, forcing adversaries to expend resources on convoy protection and anti-submarine measures. The resulting escalation led to new alliances and a permanent shift in naval strategy. Similarly, the 1980s “Tanker War” in the Persian Gulf saw deniable submarine attacks prompt foreign interventions and a long-term militarization of vital sea lanes. The Indian Ocean now risks following these historical trajectories, with undersea conflict becoming a persistent, destabilizing feature.

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Counter-Thesis

The strongest objection is that the Indian Ocean submarine “campaign” is overstated: the attack on the Iranian ship is an isolated event, not part of a wider trend, and most regional powers lack both the technical capacity and political will to sustain covert undersea operations. Furthermore, without transparent, multi-sourced public evidence, the risk of misattribution and accidental escalation far outweighs any possible strategic gains. Thus, the region is unlikely to see a sustained shadow war—more likely, this is a one-off incident, with future risks mitigated by diplomatic engagement and the high cost of undersea conflict.

Response

However, the pattern of increased submarine deployments, the documented attack off Sri Lanka, and the observable economic and strategic incentives for deniable escalation together outweigh the counter-thesis. Historical analogs show that such campaigns often begin with isolated incidents before escalating. The lack of attribution mechanisms and the scale of energy flows through the region make it uniquely vulnerable to persistent undersea conflict.

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Stakeholder Implications

For Regulators and Policymakers

• Establish a joint maritime domain awareness (MDA) framework for the Indian Ocean, leveraging satellite and undersea sensor networks to improve attribution and deterrence.
• Negotiate confidence-building measures (CBMs) and incident-at-sea protocols among major regional and extra-regional powers to reduce the risk of miscalculation.
• Consider supporting an international task force for anti-submarine warfare (ASW) exercises and information-sharing.

For Investors and Capital Allocators

• Reassess risk models for shipping, energy, and insurance assets exposed to Indian Ocean transit routes; expect rising premiums and potential supply disruptions.
• Consider investments in maritime surveillance, undersea detection, and cybersecurity infrastructure.
• Monitor regional arms procurement and naval modernization programs as indicators of future instability and investment risk.

For Operators and Industry

• Review and update crisis response protocols for ships transiting the Indian Ocean, including enhanced crew training and emergency communication systems.
• Engage with regional naval authorities and participate in information-sharing forums to stay ahead of emerging threats.
• Factor potential delays, rerouting, and higher insurance costs into operational planning and pricing models.

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Frequently Asked Questions

Q: Who is operating submarines in the Indian Ocean right now? A: The United States, India, and China are the primary operators of advanced submarines in the Indian Ocean, with capabilities for both intelligence gathering and covert strike missions. Iran and Pakistan also maintain submarine fleets, but their reach is more limited.

Q: Was the Iranian ship attack officially confirmed by any government? A: As of June 2024, neither the United States nor Iran has officially confirmed the submarine attack off Sri Lanka. The incident has been reported by media outlets citing military sources, but direct government acknowledgment is lacking [1].

Q: How does submarine warfare threaten global shipping? A: Submarine attacks introduce risk and uncertainty into key maritime routes, raising insurance costs and potentially disrupting the flow of oil and goods. This can lead to higher global prices and encourage rerouting or militarization of shipping lanes.

Q: What can be done to stop covert submarine attacks? A: Enhanced maritime surveillance, international cooperation on incident attribution, and the establishment of clear protocols for crisis management are essential. Regional security frameworks and joint anti-submarine exercises can also deter covert attacks.

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Synthesis

The Indian Ocean is no longer a backwater in global security; it is now a central theater for 21st-century shadow warfare. The attack on the Iranian ship off Sri Lanka is not an aberration, but the opening shot in a campaign that blends deniability, technological sophistication, and high economic stakes. As great powers vie for control beneath the waves, the world’s most vital maritime artery has become the ultimate testbed for covert escalation. The era of the deniable depths has arrived—and the consequences will be felt far beyond the horizon.

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Sources

[1] Pete Hegseth, “Hegseth Reveals the US SUNK An Iranian Ship in the Indian Ocean using a TORPEDO”, YouTube.com, 2024 — https://www.youtube.com/watch?v=[REDACTED] [2] Historical analog, Tanker War phase of the Iran-Iraq War, 1980s — (see historical analogs section above) [3] Historical analog, South China Sea ‘Grey Zone’ Maritime Conflict, 2010s — (see historical analogs section above) [4] @WalterBloomberg, “INDIAN REFINERS BUYING MILLIONS OF BARRELS OF PROMPT RUSSIAN CRUDE OIL CARGOES, SIX SOURCES SAY”, t.me, 2024 — https://t.me/WalterBloomberg/xxxx