What is Milan 2026, Indian Navy’s maritime exercise in which Iranian frigate IRIS Dena, sunk by US took part?

At least 87 people have been confirmed dead, while many more are unaccounted for after a US submarine struck IRIS Dena, an Iranian frigate off the coast of Sri Lanka on Wednesday. While the Sri Lankan Navy rescued 32 Iranian sailors, an estimated 60 people on board remain unaccounted for.

The sinking of IRIS Dena was the first time since World War II that a US submarine had sunk another vessel using a torpedo.

IRIS Dena, which was launched in 2015 and commissioned into the Iranian Navy in 2021, was a destroyer equipped with four Iran-made engines "Bonyan 4" and a vertical launching system.

It was one of the warships that took part in the recently concluded Milan 2026 in Visakhapatnam in the Indian Ocean.

According to the Indian Navy, Milan 2026 saw the participation of 74 countries, making it the largest and most inclusive to date, with Germany, the Philippines, and the UAE participating with military assets for the first time.

These exercises provide a platform for participating nations to learn and practice joint maritime combat strategies and interoperability, the Navy said.

"Held under the theme 'Camaraderie, Cooperation, Collaboration', The Milan 2026 witnessed participation on an unprecedented scale, comprising 42 ships and submarines and, 29 aircraft. These also included 18 ships from the participating friendly foreign countries," the Indian Navy said.

The mega exercise was held for over a week and culminated with a closing ceremony held onboard India's indigenous aircraft carrier INS Vikrant off the coast of Visakhapatnam.

The exercise comprised both a harbour phase that featured bilateral engagements and an international maritime seminar and a 'Sea Phase', which included high-intensity operational drills focused on advanced warfare disciplines, including integrated air defence and antisubmarine warfare exercises, maritime interdiction operations, communication exercises, and cross-deck flying operations.

The objectives of the exercise included enhancing the ability of diverse navies to operate together as a cohesive force and focusing on collective responses to non-traditional threats like piracy and drone swarms.

According to reports, this was the second time IRIS Dena was part of Milan. The Iranian warship also took part in the 12th edition of Milan in 2024.

Caine said the US has sunk Dena, over 20 Iranian vessels and an Iranian submarine since Saturday, when the US-Israel Operation Epic Fury began.

“We’ve destroyed more than 20 Iranian naval vessels, in addition to the frigate outside the area, one submarine and effectively neutralized at this point in time Iran’s major naval presence in theater out there,” he said.