Operation Epic Fury has seen extensive U.S. military action against the Iranian regime within Iran’s borders. Precision air and naval strikes have struck command and control centers, ballistic missile sites, and even Iranian Navy vessels. While these types of military actions have been seen in modern combat, the Pentagon confirmed an action that the United States hasn’t conducted in decades: a submarine torpedo kill.
Related: How Kuwait’s air defenses downed three American F-15 Strike Eagles
On the morning of March 4, 2026, Defense Secretary Pete Hegseth delivered a press briefing in which he confirmed that a U.S. submarine sunk an Iranian warship. “In the Indian Ocean—an American submarine sunk an Iranian warship, that thought it was safe in international waters. Instead, it was sunk by a torpedo—Quiet Death,” Hegseth said. “The first sinking of an enemy ship by a torpedo since World War 2. Like in that war—back when we were still the War Department—we are fighting to win.”
While the identity of the U.S. submarine was not identified for operational security, the IRIS (Islamic Republic of Iran Navy) Dena was in the region off the southern coast of Sri Lanka. The Moudge-class frigate is assigned to the Iranian Navy’s Southern Fleet and had reportedly taken part in a naval drill in the Bay of Bengal.
Sri Lankan Foreign Minister Vijitha Herath reported that 180 personnel were aboard the IRIS Dena and that 32 survivors were rescued by the Sri Lankan Navy. A Sri Lankan Navy spokesman also noted that the rescue effort recovered bodies from the scene.
In the video released by the Pentagon, the stern of the targeted ship is lifted out of the water by the force of the munition blast. The catastrophic failure of the hull’s integrity causes the ship to immediately begin sinking.
“For the first time since 1945, a United States Navy fast attack submarine has sunk an enemy combatant ship using a single Mark 48 torpedo to achieve immediate effect, sending the warship to the bottom of the sea,” Chairman of the Joint Chiefs of Staff Gen. Dan Caine said at the press briefing. “This is an incredible demonstration of America’s global reach. To hunt, find, and kill an out-of-area deployer is something that only the United States can do at this time of scale.”
First introduced in 1972, the Mark 48 is a heavyweight submarine-launched torpedo designed to engage both surface and subsurface targets. Able to be guided from the firing submarine via wires, the latest Mod 7 version of the torpedo also has an advanced, onboard sonar guidance system and is resistant to electronic countermeasures.
The Mark 48 is carried by all U.S. Navy submarines. Currently, the fast attack fleet includes the Los Angeles, Seawolf, and Virginia class submarines. While not identified as the class of ship that sunk the IRIS Dena, the Ohio-class ballistic missile submarines can also carry the Mark 48.
Operation Epic Fury kicked off on February 28, 2026. Since then, Caine reports that more than 2,000 targets have been struck across Iran and more than 20 Iranian Navy ships have been destroyed. The U.S. lost three F-15E Strike Eagles to friendly fire from Kuwaiti air defenses, though all crew members ejected and survived. Six U.S. service members assigned to the 103rd Sustainment Command were killed following an unmanned drone attack in Port Shuaiba, Kuwait, on March 1, 2026. As of the writing of this article, four of the six soldiers have been identified: Capt. Cody Khork, Sgt. 1st Class Noah Tietjens, Sgt. 1st Class Nicole Amor, and Sgt. Declan Coady. The Pentagon reports that the incident is under investigation.
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