IRIS Dena was a Moudge-class frigate1 in the Southern Fleet of the Islamic Republic of Iran Navy, named after Mount Dena. Secretary of War Pete Hegseth said on March 4, 2026 that the Iranian ship had been sunk in the Indian Ocean by a torpedo fired from a US Navy submarine. Seapower Magazine describes the action as the first sinking of an enemy warship by a US submarine’s torpedo2 since World War II.
Design and construction
The Moudge, or Mowj, is a class of domestically produced Iranian light frigates3. The class appeared to be a development of the Alvand class4, and Iran officially classifies these ships as destroyers, a label most navies reject. English-language media described Dena as both a destroyer and a frigate; in Persian she was a novshekan, which translates to “destroyer”.
Dena was launched in 2015 and commissioned into the Iranian Navy in 20211. She was the first Iranian ship equipped with the Iranian “Bonyan 4” engines and had a bow thruster system for better maneuverability.
According to Iranian Navy Commander Hossein Khanzadi, the ship carried a significantly greater armament than the frigates of the same class. Statements from 20191 said Dena would receive a vertical launching system, a first for an Iranian ship. She was eventually fitted with two Sayyad missiles instead, and photographs show two container launchers before the bridge, as on earlier ships of the class.
Specifications
Army Recognition gives the Moudge class a displacement of 1,500 tonnes, a beam of 11.1 m and a draught of 3.25 m. She had four engines, each generating 5,000 hp1. The class has a top speed of 30 knots and a crew complement of 140, and its ships carry the Asr 3D PESA long-range radar3. Like the other ships of her class, Dena had a landing pad for a helicopter.
Her listed armament was four Ghader anti-ship missiles, a 76 mm Fajr-27 naval gun1, a 40 mm Fath-40 AA cannon, two 20 mm Oerlikon cannons, two 12.7 mm heavy machine guns and two triple 324 mm anti-submarine torpedo launchers. For air defense, the Moudge class carries four Mehrab SAMs, a naval version of the Sayyad-23.
Service history
In 2022–20231, Dena and IRIS Makran of the 86th naval fleet sailed the 360-Degree mission around the world, a historic mission for the Iranian Navy. Despite American pressure, the two ships were able to dock in Rio de Janeiro, Brazil3.
In February 20261, Dena took part in the International Fleet Review 2026 at the Indian port of Visakhapatnam. On 26 February5, the Iranian embassy in Sri Lanka requested a “goodwill visit” for Dena and two other ships. After US and Israeli airstrikes on Iran began, the Sri Lankan government told Iran it would let ships at war dock only in an emergency.
Fate
According to Sri Lanka’s Ministry of Foreign Affairs, Dena sent a distress call at 05:08 Sri Lanka time on 4 March 20265, reporting an explosion. She was returning to Iran from India, off Galle, Sri Lanka, in international waters. A US official stated that the United States gave no warning before the strike. US officials named the submarine as USS Charlotte, which fired two Mark 48 torpedoes, of which one hit Dena1. US Navy submarines are armed with the 21-inch Mark 48 torpedo. Seapower Magazine reported that the BBC identified the ship as one of six ships of the Moudge class2 and that she went down off the southern coast of Sri Lanka.
Casualty figures differ by source. In a report dated March 4, 2026, Seapower Magazine, citing Reuters, said that the Sri Lankan Navy rescued 32 people from a crew estimated at 180, and that at least 80 crew members died2. Later reports put the crew at 136: 104 killed, 20 of them never recovered, and 32 survivors5. The survivors were taken to Galle National Hospital.
The ship was reportedly unarmed or lightly armed at the time because of her part in the fleet review, but US Indo-Pacific Command denied that Dena was unarmed5. In a post on X, the command said the ship was armed, that her destruction was that of a valid military target, and that it had planned for Sri Lankan rescue operations in line with international law. The government of Iran called the attack “an atrocity at sea”. The sinking sparked debate over whether US forces, by leaving without attempting to rescue survivors, broke the Second Geneva Convention.
Seapower Magazine compared the sinking with an earlier one: on May 2, 19822, during the Falklands War, the Royal Navy nuclear-powered attack submarine HMS Conqueror sank the Argentine Navy cruiser ARA Belgrano with a torpedo.
Sister ships and similar ships
- Jamaran: the first ship of the Moudge class4, stationed at Bandar Abbas like Dena.
- Damavand: the second ship of the class, built at Bandar-e Anzali on the Caspian Sea; she ran aground near her home port in January 20184.
- Alvand class: the Moudge design is a modified Iranian-built version of the Alvand class. The four Alvand ships were built in the United Kingdom by Vosper and, unlike Dena’s all-diesel plant, added two Rolls-Royce Olympus gas turbines for a speed of 39 knots6.