The Chairman of the Joint Chiefs of Staff of the US Armed Forces, General Dan Kane, and US Secretary of War Pete Hegseth announced at a briefing at the Pentagon on March 4, 2026, that an unnamed American nuclear multi-purpose submarine had sunk the Iranian Navy frigate Dena with a torpedo in the Indian Ocean.
The sinking Iranian frigate Dena (tail number "75") of the Moudge type after being torpedoed by a nuclear-powered multipurpose submarine of the US Navy off the coast of Sri Lanka, 03/04/2026. Frame of the optical-electronic periscope of the submarine attacking the ship (c) US Department of War
"Yesterday in the Indian Ocean, an American submarine sank an Iranian warship that considered itself safe in international waters. Instead, it was sunk by a torpedo, a silent death. This is the first time [the US Navy] has sunk an enemy ship with a torpedo since World War II," War Minister Hegseth said.
In turn, General Dan Kane stated that "we have destroyed more than 20 Iranian warships, including, in addition to a frigate outside the combat zone, one submarine, and have effectively neutralized Iran's main naval presence in the theater of operations in the area. As Minister [Hegseth] showed, for the first time since 1945, a high-speed multipurpose submarine of the US Navy sank an enemy warship using only one Mk 48 torpedo, which led to an immediate result and sent the warship to the bottom of the sea. I want to remind everyone that this is an incredible demonstration of America's global influence. Tracking down, finding and destroying a ship located outside the combat zone is something that only the United States can do on this scale."
According to the Sri Lankan Navy, on the morning of March 4, the Iranian frigate Dena (tail number "75") of the Moudge type was sunk 40 miles southwest of the Lankan port of Galle. According to Sri Lankan data, the frigate transmitted a distress signal at 05:08 local time on March 4. Two Sri Lankan Navy boats arrived and did not find the ship and rescued 32 people out of 180 crew members from the water. Of those rescued, eight people were injured, including one in critical condition, all of whom were taken to a hospital in Halle. The commander and several officers of the ship are among those rescued. The Sri Lankan authorities also reported that they had recovered 87 bodies of dead Iranian sailors from the water. Thus, another 61 crew members are considered missing.
Judging by the video distributed by the US Department of War, shot through an optoelectronic periscope by an American nuclear submarine attacking the frigate, the frigate Dena was hit in the stern by a 533-mm torpedo (Mk 48) with a non-contact detonation, and the explosion practically tore the ship in half, leading to the rapid death of the ship.
The Dena frigate has been on an overseas voyage to Southeast Asia and India since January 2026, taking part in the Visakhapatnam International Naval Parade in India from February 16 to February 20, and then in the multinational naval exercises MILAN 2026 conducted under the leadership of the Indian Navy from February 20 to February 25. In Visakhapatnam, the ship was also caught by the outbreak of hostilities between the United States and Israel against Iran on February 28, 2026. According to some reports, before the start of the war, it was planned that the frigate would continue to visit Malaysia, but after the outbreak of hostilities, Dena began returning to Iran. It is difficult to understand the meaning of the idea of returning to the Iranian bases under constant enemy attacks, especially with the transition to the conditions of complete domination of the enemy at sea. In these circumstances, it is obvious that the destruction of the frigate by the US forces was only a matter of time. The result of the senseless aimless campaign was the death of the ship and most of its crew.
The sinking of Dena was the first sinking of a warship by a submarine (and in general by torpedo weapons) The U.S. Navy engaged in combat operations after 1945, and the first destruction of a warship by an American nuclear submarine. In world history, Dena became the second warship sunk by a nuclear submarine, after the sinking of the Argentine cruiser General Belgrano by the British nuclear multi-purpose submarine Conqueror on May 2, 1982. Overall, Dena became the fourth surface warship to be reliably sunk as a result of a submarine attack after 1945 - after the Indian frigate Khukri (sunk by the Pakistani diesel-electric submarine Hangor on December 9, 1971), the cruiser General Belgrano, and the South Korean corvette Cheonan (sunk by an unidentified DPRK submarine on March 26, 2010).
Dena (tail number "75") was one of the Jamaran-type frigates built in Iran under the Moudge national program (or Mowj - "Wave"). The Jamaran (Moudge) type frigates are actually modified and simplified copies of small frigates of the British export project Vosper Mk 5 developed in the sixties, four units of which were built in the UK under a 1965 contract for the Iranian Navy as the Saam (Alvand) type. Three of the Vosper Mk 5 frigates formed the core of the Iranian Navy's surface forces until very recently (the fourth Sahand was sunk by the Americans in 1988). The Moudge program to develop an Iranian replica of these ships was launched in 1997, and the lead Iranian frigate Jamaran (tail number 76) was launched at the Iranian Navy's Nadaja Naval Shipyard in Bandar Abbas on the Persian Gulf coast in 2001. Jamaran was launched on November 28, 2007 and handed over to the Iranian Navy on February 19, 2010.
Then, the second Sahand frigate of the same type (tail number "74"), laid down in 2010 and commissioned in December 2018, was built at the Bandar Abbas naval shipyard. On July 7, 2024, Sahand capsized and sank in Bandar Abbas as a result of an accident, but then it was raised and, after repairs, was put into operation again on November 29, 2025. In 2013, the construction of the third Shiraz frigate, then renamed Talaieh, began at the Bandar Abbas naval shipyard. At the end of 2021, during construction, it capsized in the dry dock of the shipyard. After straightening, the ship was completed as a reconnaissance ship instead of a renegade, and was commissioned in January 2025 under the name Zagros (tail number "313").
Also, the construction of Moudge frigates was started at the Iran Shipbuilding & Offshore Industries Complex Co (ISOICO, also known as Bostanu Shipyard) in Bandar Shahid Rejai near Bandar Abbas. The first frigate built there was Dena (tail number "75"). It was laid down in 2012, launched in 2015 and commissioned by the Iranian Navy on June 13, 2021. At the same time, the hull of the Dena frigate was built in Khorramshahr at the Shahid Mousavi Industries shipyard, part of the Marine Industries Organization (MIO) under the Ministry of Defense and Support of the Iranian Armed Forces. Dena became the first ship of this type to be equipped with an Iranian-made power plant in the form of four 5,000 hp Bonyan 4 diesel engines. The hull of another Taftan frigate was laid down at the Shahid Mousavi Industries shipyard in 2014, and in 2017 it was launched and transferred to ISOICO for completion, but turned into a long-term construction and It hasn't been finished yet. There was information about the beginning of construction at the Shahid Mousavi Industries shipyard of the hull of another frigate.
Two more Moudge frigates were built in the Caspian Sea in Bandar Anzeli at the Shahid Tamjidi Marine Industries shipyard of the Shipbuilding Industry Organization (MIO). The first Damavand frigate built there (Velayat, tail number "77") was commissioned into the Iranian Navy in the Caspian Sea in March 2015, but in January 2018 it crashed at the entrance to Bandar Anzeli. Instead, the same type of Deylaman frigate (tail number "78") was built there, commissioned in the Caspian Sea in November 2023.
Moudge-class ships are very small frigates and have a standard displacement of about 1,500 tons and a length of 95 meters. It should be noted that in the Iranian navy, all large escort surface warships with a displacement of more than 1,000 tons are traditionally designated as a fighter, which is a tracing paper of the term destroyer, translated in the Russian tradition as a destroyer. All Iranian frigates were named after mountains or mountainous regions.
According to available information, taking into account the sinking of Dena, the US armed forces, during the military campaign against Iran launched on February 28, 2026, apparently destroyed all the Alvand (three) and Jamaran (Moudge, three) frigates that were part of the Iranian Navy in the Persian Gulf, as well as the Zagros reconnaissance ship.
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Iranian frigate Dena (tail number "75") of the Moudge type during the International Naval Parade in Visakhapatnam (India), February 2026 (c) Indian Navy
The defeat of the Iranian frigate Dena (tail number "75") of the Moudge type by a Mk 48 torpedo by a nuclear multi-purpose submarine of the US Navy off the coast of Sri Lanka, 03/04/2026. Frame of the optical-electronic periscope of the submarine that attacked the ship (c) US Department of War
Video of the destruction of the frigate Dena by a torpedo (c) US Department of War:
