'Quiet Death' In The Indian Ocean: How America's Lethal Mark 48 Torpedo Sank An Iranian Warship

Last Updated:March 05, 2026, 12:17 IST

The Mark 48 is a state-of-the-art heavyweight torpedo with a 650-pound warhead, capable of tracking and engaging surface ships and submarines with extreme precision

A US Los Angeles-class fast-attack submarine sank an Iranian warship in the Indian Ocean this week, marking the first time an American submarine has destroyed an enemy vessel since World War II. The attack, carried out with a Mark 48 torpedo, was touted by US Defence Secretary Pete Hegseth as evidence of America’s global reach in its war on Iran.

“An American submarine sunk an Iranian warship that thought it was safe in international waters. Instead, it was sunk by a torpedo," Hegseth told a news conference.

THE MARK 48 TORPEDO

The Mark 48 is a state-of-the-art heavyweight torpedo with a 650-pound warhead, capable of tracking and engaging surface ships and submarines with extreme precision. It measures about 19 feet in length, 21 inches in diameter and weighs around 3,700 pounds. Unlike the unguided torpedoes of World War II, it can home in on targets using active or passive sonar, operate with or without wire guidance, and reengage if it misses, making it “barely even the same species" as its historical counterparts, according to James Holmes, the JC Wylie Chair of Maritime Strategy at the US Naval War College. “The Mark 48 is optimal for engaging enemy submarines, giving it a whole new operating dimension," Holmes said.

According to Sri Lanka Guardian, unlike most anti-ship missiles that strike a vessel above the waterline, the Mark 48 torpedo is designed to explode beneath the ship’s hull, targeting one of the most vulnerable points in naval design.

When the warhead detonates under a vessel, it generates a massive gas bubble that rapidly expands and then collapses. The initial surge can lift thousands of tons of steel out of the water, while the collapse removes the support that keeps the hull afloat, causing it to bend, crack, or even break in two. Even if the ship’s structure remains intact, critical systems, like propulsion shafts, bulkheads, and electronics, are often destroyed, leaving the vessel crippled or completely inoperable.

Retired Navy Captain Thomas Shugart, a former submariner, described the strike as overwhelmingly effective. “This ship didn’t have a chance… it probably had no idea the submarine was there. It had no way to see the weapon coming. It’s probably the most assured way to sink a ship like that, but also the most punishing," he told Task & Purpose, an American digital news and media organisation that covers the US military, veterans, and the defence industry.

General Dan Caine, chairman of the Joint Chiefs of Staff, confirmed that the Mark 48 torpedo was used to neutralise the Iranian frigate IRIS Dena, one of more than 20 vessels destroyed as part of the US-Israeli military campaign against Iran. The strike also demonstrated the US Navy’s ability to operate far from home waters against a modern warship equipped with long-range missiles, without risking aircraft or surface vessels—an attack that Hegseth called the “quiet death".

The Mark 48 torpedo, costing roughly $4.2 million per unit, is designed to deliver devastating effect against heavily armed ships. Experts say its use in this strike highlights a significant return of submarines to offensive operations after decades of primarily surveillance and deterrence roles. Retired Navy Captain Bent Sadler, speaking to Task & Purpose, noted: “The strongest use of submarines is unleashing the captains of those boats with a set of orders: Go in this area and kill anything that meets the following conditions, and act as you see fit."

Sri Lankan authorities rescued 32 crew members from the frigate, though 148 sailors remain missing. The ship sank less than an hour after issuing a distress call 40 kilometers south of Galle, leaving only an oil patch at the site, according to AFP.

IRAN SEES RED

Following the naval attack, Iran’s Foreign Minister Seyed Abbas Araghchi on Thursday warned the United States that it will “bitterly regret" its action. In a post on X, Araghchi said the United States had carried out “an atrocity at sea" far from Iran’s shores. He stated that the frigate Dena, carrying nearly 130 sailors, was a “guest" of the Indian Navy and was attacked in international waters without warning.

The vessel was returning home using a standard westward route after taking part in India’s MILAN 2026 multinational naval exercise and International Fleet Review in Visakhapatnam weeks earlier.

News explainers 'Quiet Death' In The Indian Ocean: How America's Lethal Mark 48 Torpedo Sank An Iranian Warship

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