The Iranian frigate IRIS Dena had just left Exercise MILAN, a multinational Indian Navy exercise involving ships from 74 nations, when a U.S. submarine fired a single Mark 48 torpedo into her hull south of Sri Lanka on March 4. The blast killed over 80 of her approximately 180-man crew. Thirty-two survivors were pulled from the water by Sri Lanka's navy. The rest are still missing.
The submarine departed without attempting a rescue or alerting anyone. Congress never authorized the war. The ship had just participated in naval exercises alongside American personnel. And the ship, some argue, may have been unarmed.
International law scholars, former Pentagon officials and members of Congress have since debated whether the strike was legal, whether the U.S. violated its obligations under the Geneva Convention by leaving survivors in the water and whether the president had constitutional authority to order the campaign in the first place.
Was the Ship a Legitimate Target?
Iran's government moved quickly to characterize the Dena as defenseless. Iran's ambassador to India told reporters the ship was "unarmed and in a regular maneuver at sea."
Former Indian diplomat Kanwal Sibal, who served as India's foreign secretary from 2002 to 2003, amplified the claim on social media, asserting that MILAN placed participating ships under "peace protocol" barring them from carrying live ammunition.
Sibal produced no proof for that assertion. India's own official record complicates the claims even further.
The Press Information Bureau, India's government press office, published a detailed account of MILAN 2026's sea phase confirming that "live firings as part of surface gun shoots, as well as anti-air firings, were also undertaken" by participating vessels. If a blanket ammunition ban governed the exercise, it was not reflected in the account India itself provided.
Whether the Dena specifically had her weapons systems loaded when she departed Visakhapatnam on Feb. 25 remains unconfirmed by any official source on either side.
Under the law of naval warfare, the question may be beside the point. A warship's status as a lawful military target derives from its flag and its function in a conflict, not the state of her magazines at a given moment. Under the same laws, even unarmed merchant vessels flying an enemy flag can be sunk during armed conflict, provided certain conditions are met, including visit and search procedures in some cases.
The Dena was an Iranian Navy war vessel transiting the Indian Ocean while her country was in open conflict with the United States. As such, a warship flying an enemy flag is a valid military target, but whether the United States was lawfully at war is a question the strike off Sri Lanka has forced into open debate.
Wes Bryant, a former Air Force special operations targeting expert and former chief of civilian harm assessments at the Pentagon, called the strike illegal.
"Was that warship actively posing a threat or participating in hostilities?" Bryant said. "You cannot say that this warship was an imminent threat to anyone. By targeting it, is the Trump administration saying that the imminent threat is all of Iran's government and military? If so, that's an incredibly dangerous example of military overreach."
The P-8A Question
USS Pinckney, a Navy destroyer originally slated to represent the United States at MILAN, diverted to Singapore on Feb. 15 before the exercise began, as Operation Epic Fury was taking shape.
A single P-8A Poseidon maritime patrol and reconnaissance aircraft from Patrol Squadron 4 remained and flew the full exercise from Feb. 17-26, according to an official Navy press release.
According to Boeing's published specifications and Department of Defense program documentation, the aircraft is purpose-built to search, detect, classify, localize, track and attack submarines using sonobuoys, inverse synthetic aperture radar and an integrated acoustic sensor suite.
The Navy left its premier maritime patrol and anti-submarine warfare platform to fly drills alongside Iranian naval assets, including the Dena, before the war began. Whether that was coincidence, or whether the P-8A was building a targeting picture it would later share with the submarine, is a question the Pentagon has not answered. No official source has alleged a direct connection.
No legal framework clearly prohibits using intelligence gathered during a multilateral exercise to later target a participating ship. There is also no modern precedent for it. If data gathered during the exercise or after contributed to the strike, it would not necessarily constitute a violation of international law.
It would, however, represent something without parallel in the history of multinational naval cooperation, almost certainly executed without India's knowledge or consent. For a country that spent years building MILAN into a cornerstone of its maritime diplomacy, that possibility alone may prove more damaging to U.S.-India relations than the sinking itself.
Indian officials have already expressed concern over the strike as it occurred near Indian shores and so shortly after the ship participated in the multi-national naval exercises. American officials have conversely argued any enemy vessel is a legitimate target, regardless of what its last port call was.
Why the Submarine Did Not Rescue Survivors
The U.S. submarine departed after firing. Sri Lanka's navy received the Dena's distress call at 5:08 a.m. local time, launched a joint operation with the air force and brought survivors and bodies to Galle. More than 100 crew members remain unaccounted for.
Article 18 of the Second Geneva Convention requires parties to a conflict to search for and collect shipwrecked personnel after naval engagements, to the extent military circumstances permit. Critics have argued the U.S. submarine violated that obligation by departing the scene.
The history behind that language is directly relevant. At the Nuremberg tribunals, German Admiral Karl Doenitz faced a version of this charge for issuing the Laconia Order, directing U-boat commanders not to rescue survivors after Allied aircraft repeatedly attacked submarines that surfaced to do so.
American Admiral Chester Nimitz submitted a written declaration to the tribunal confirming U.S. submarines in the Pacific had operated under the same standing orders for the same reasons. Doenitz was not convicted on that specific charge.
The physical constraints that drove those WWII-era orders have not changed. A fast-attack submarine carries roughly 130 of its own crew in a sealed pressure vessel with no mass-casualty medical capability and no means to accommodate dozens of blast or burn-injured survivors. Surfacing exposes the boat to detection and potential attack.
Even alerting nearby vessels or nations to the sinking could lead to potential danger for the submarine. This is relevant as Sri Lankan officials noted another Iranian vessel was operating in the area.
The conditional language of Article 18 itself makes the question genuinely unsettled. The obligation requires rescue only to the extent military circumstances permit. Whether those circumstances were met south of Sri Lanka, in uncontested waters far from active fighting, is a question legal scholars have begun to raise. The Pentagon has not addressed it publicly.
Congress and the Constitutional Dispute
Operation Epic Fury launched without a declaration of war or an Authorization for Use of Military Force. The Senate voted 47-53 on Wednesday to reject a war powers resolution sponsored by Democratic Sen. Tim Kaine of Virginia and Republican Sen. Rand Paul of Kentucky. Paul was the only Republican to cross party lines. Democratic Sen. John Fetterman of Pennsylvania was the only member of his party to vote against it.
The House followed Thursday, defeating a companion resolution sponsored by Rep. Ro Khanna, D-Calif., and Rep. Thomas Massie, R-Ky., by a vote of 212-219. Four Democrats crossed the aisle to vote against it. Only Massie and Rep. Warren Davidson of Ohio broke from Republicans to support it.
Secretary of State Marco Rubio told reporters the administration complied fully with the 1973 War Powers Resolution while asserting the law itself is unconstitutional.
"We complied with the law 100%, and we're going to continue to comply with it," Rubio said.
Presidents of both parties have launched major military operations without formal war declarations since Korea. Both chambers of Congress have now declined to challenge that precedent.
The sinking of the IRIS Dena was legal under the law of naval warfare, the submarine was neither required nor equipped to rescue the sailors it left in the water, and Congress had every opportunity to stop the war but voted against it. What remains harder to explain is why the U.S. left its premier submarine-hunting aircraft to fly drills alongside the Dena one week before a submarine killed her.
