US submarine sinks Iranian warship by torpedo
Secretary of War Pete Hegseth said Wednesday that an American submarine torpedo sank an Iranian warship in international waters in a first since World War II.
A multi-million-dollar U.S. Navy torpedo detonated underneath an Iranian warship in a nighttime submarine strike off Sri Lanka’s southern coast — an attack, Defense Secretary Pete Hegseth said Wednesday in a Pentagon update, was the first of its kind since World War II.
The weapon, identified as a Mark 48 Advanced Capability (ADCAP) torpedo, underscored the scale of force used, and signaled to Tehran that "the gloves really are off," according to a former U.S. submarine commander.
"The Mark 48 is one of the most lethal anti-ship weapons in the U.S. inventory," Thomas Shugart, an adjunct senior fellow at the Center for a New American Security, told Fox News Digital.
The torpedo carries an 800-pound warhead and is designed not to strike a ship directly, Shugart said, but to detonate beneath it, creating a massive vapor bubble that breaks the vessel’s back and splits it in half.
A U.S. submarine sunk an Iranian warship in international waters in the Indian Ocean, War Secretary Pete Hegseth confirmed Wednesday. (@DeptofWar / X)
"This torpedo detonated underneath the stern of the Iranian ship and lifted it up out of the water, and so it sank in a matter of minutes," he added.
The torpedo costs approximately $4.2 million per unit, according to recent data, with Shugart likening the strike to rare submarine attacks in modern naval history.
In addition to World War II, he pointed to the 1982 Falklands War as one example of a submarine-launched torpedo sinking a major surface combatant.
"This was the second time ever that a nuclear-powered submarine has fired a torpedo and sunk a ship," Shugart said.
"The only other time that happened was a British submarine called HMS Conqueror, which similarly sank an Argentine cruiser, the General Belgrano, during the Falklands War in 1982," he added.
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Pete Hegseth, President-elect Donald Trump's choice to be Defense secretary, at the completion of his confirmation hearing before the Senate Armed Services Committee, at the Capitol in Washington, Tuesday, Jan. 14, 2025. (AP Photo/Ben Curtis) (AP Photo/Ben Curtis)
The naval submarine operation, he said, would have involved increased surveillance, forward naval deployments and targeted actions designed to demonstrate U.S. maritime dominance.
"It definitely seems to me like a message that the gloves really are off," Shugart added.
"There are other ways that the U.S. military could have disabled that ship or even sunk it, but in a manner that I wouldn't say was more merciful, but in a manner that wasn't quite as violent and without any warning."
"An American submarine sank an Iranian warship that thought it was safe in international waters," Hegseth said at the Wednesday briefing.
In this photo provided by U.S. Navy, the Los Angeles-class fast attack submarine USS Oklahoma City (SSN 723) returns to U.S. Naval Base in Guam, Aug. 19, 2021. (Mass Communication Specialist 3rd Class Naomi Johnson/U.S. Navy via AP)
Hesgeth described the strike as "a quiet death," adding that it marked the first sinking of an enemy ship by torpedo since World War II.
"The U.S. Navy submarines are very highly mobile, very, very quiet, and our crews are extremely well-trained," Shugart explained. "This was not a challenge for a U.S. Navy submarine to fire a torpedo."
"To hunt down and sink an Iranian ship like that is not — that's not a challenging task for a U.S. nuclear-powered submarine," he said.
The targeted vessel, identified as the IRIS Dena, was the newest frigate in Iran’s naval fleet and was equipped with surface-to-air missiles, anti-ship missiles, torpedo launchers and other heavy weaponry.
According to Sri Lanka’s Foreign Affairs Minister Vijitha Herath, the country’s coast guard received a distress call at 5:08 a.m. local time Wednesday from the Iranian vessel reporting an explosion.
Healthcare workers unload the bodies of Iranian sailors from a vehicle who died when their IRIS Dena warship sank outside Sri Lanka's territorial waters, in Galle, Sri Lanka, Wednesday, March 4, 2026. (AP Photo/Eranga Jayawardena)
"I'm not sure Iran has any operational submarines anymore, but if they were operational, their biggest submarines would be at least 20 or 30 years old," Shugart said.
"They would be ex-Russian diesel-electric submarines, so they're not nuclear-powered like the U.S. ones, with satellite communications and unlimited mobility."
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"They can operate at high speed for as long as they want with unlimited endurance, other than the food on board. They carry the most advanced weapons, the most advanced sensors."
"This strike sent a message that if there are any Iranian warships left or any Iranian government-owned ships, they should expect no mercy," he added.
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