A US nuclear attack submarine achieved a rare wartime feat in the Indian Ocean this month by sinking an Iranian frigate off the coast of Sri Lanka. This marked the first instance since the Second World War that a US submarine had destroyed another vessel using a torpedo, reported Asia Times.

The target was the 1,500-ton Moudge-class frigate IRIS Dena (75). An MK-48 heavyweight torpedo struck the ship, breaking its keel and sending it to the seabed. General Dan Caine, Chairman of the Joint Chiefs of Staff, confirmed these details during a US Department of Defence briefing.

US Defence Secretary Pete Hegseth explained that the frigate had been operating in international waters following exercises in the Bay of Bengal. The strike formed part of the broader US-Israel 'Operation Epic Fury' campaign against Iran.

Since the operation's launch, the US has sunk over 20 Iranian vessels and one submarine. This has significantly eroded Iran's naval capabilities in the region. Video footage released by the Department of Defense captured the frigate moments before a massive underwater explosion.

Sri Lanka's navy promptly initiated search-and-rescue efforts. They rescued 32 Iranian sailors and recovered several bodies, with ongoing operations to find more survivors.

General Caine emphasised that US Central Command would persist in targeting Iranian infrastructure and naval assets. Intelligence, surveillance, and reconnaissance resources are actively hunting ballistic missile launchers and one-way attack systems.

This incident underscores the escalating strategic value of the Indian Ocean's sea lanes. It exposes vulnerabilities in China's energy supply chains from the Middle East, which are vital for its economy.

A May 2025 report from the US Energy Information Administration notes that 92 per cent of China's oil travels by sea. Only a minor share arrives via pipelines from Russia, Kazakhstan, and Myanmar.

China Power's June 2025 estimate indicates that about 80 per cent of China's non-Russian oil imports pass through the Malacca Strait. This chokepoint renders China susceptible to potential blockades.

Alternative routes exist for China, including the Lombok-Makassar Strait, Sunda Strait, Arctic Northern Sea Route, and Pacific paths from the Americas or East Siberia. These could sustain oil flows if the Malacca Strait were disrupted.

The US has long recognised these weaknesses. Its 5th Fleet in Bahrain and forces at Diego Garcia provide key leverage in the Indian Ocean. The Indian and Australian navies could support interdiction of Chinese oil shipments.

Allied forces might also target the supply lines' origins, such as the Strait of Hormuz linking the Persian Gulf to the Indian Ocean, or Bab El-Mandeb connecting the Red Sea to the Gulf of Aden.

In a December 2023 Proceedings article, Michael Hanson proposed that the US Navy position itself beyond China's weapon engagement zones to intercept vessels at these chokepoints. Submarines could prioritise China's oil tanker fleet, echoing Second World War tactics against Japanese merchant shipping.

China, alert to these risks, has bolstered its Indian Ocean footprint. Darshana Baruah's May 2025 analysis for the International Institute for Strategic Studies details China's naval deployments since 2008, submarine operations from 2014, and its first overseas base in Djibouti in 2017.

China conducts frequent exercises involving maritime, air, and land forces to familiarise itself with the region and safeguard energy and trade routes.

Chinese firms have developed or upgraded ports like Gwadar in Pakistan, Hambantota and Colombo in Sri Lanka, Kyaukphyu in Myanmar, and various East African facilities. These form a logistical network bolstering China's maritime presence.

T.X. Hammes, in a March 2025 Atlantic Council piece, argues that China could repurpose these commercial ports as military 'counter-intervention' hubs during conflict. They might pre-store command-and-control gear, missiles, electronic warfare systems, and munitions in disguised containers.

Personnel could deploy rapidly by air to activate these assets, enabling China to shield shipping, rearm vessels, and disrupt trade at chokepoints in response to a US blockade.

Questions linger over China's willingness to defend these distant outposts, which remain isolated, hard to resupply, and prone to attack.

Beyond maritime efforts, China is pursuing a continental strategy by strengthening ties with Russia. The Financial Times reported this month that Russia supplies 20 per cent of China's oil, making it the largest provider.

Longer-term options include accelerating the Power of Siberia 2 pipeline and expanding Arctic routes. However, these depend on the Ukraine conflict's resolution.

Chinese Foreign Minister Wang Yi has stated that Beijing cannot afford a Russian defeat in Ukraine. Yet avoiding loss does not guarantee victory.

A Russian defeat might free US resources for a Pacific pivot, heightening pressure on China. Conversely, a Russian win lifting Western sanctions could foster Moscow's independence, intensifying competition with China in Central Asia and the Russian Far East.

A Ukraine stalemate might suit China best, perpetuating sanctions that bind Russia economically to Beijing. This asymmetry could grant China sway over Russian energy, arms sales, Central Asian influence, and dormant territorial disputes in the Russian Far East.

The Indian Ocean is solidifying as a pivotal theatre in great-power rivalry. US naval dominance imperils China's energy lifelines, even as Beijing extends its reach and diversifies via land-based hedges.

Asia Times