Mark-48 torpedo: The lethal US submarine weapon that sent Iranian warship to the bottom of the Indian Ocean; how it works

The United States on Wednesday released a video showing the final moments of the IRIS Dena, a modern Iranian Moudge-class frigate, before it sank in the Indian Ocean.

The black-and-white infrared footage captures the moment an American submarine launched a Mark-48 heavyweight torpedo that struck and destroyed the Iranian Navy vessel.




According to US officials, the strike killed more than 80 sailors and sent the warship to the bottom of the ocean.

The incident marks one of the most dramatic naval moments in the widening crisis in the Middle East.

The sinking of the Iranian warship comes as rockets, missiles and drones continue to fly across Israel, Iran and other parts of the region, fuelling fears that the conflict could spiral into a broader regional war.

Amid the escalating tensions, attention has turned to the weapon used in the strike, the Mark-48 torpedo, the US Navy’s primary submarine-launched weapon.

Mark-48 torpedo: Key things to know about the US Navy’s lethal undersea weapon

• The Mark-48 heavyweight torpedo has long been the backbone of the US Navy’s submarine warfare capability. Designed to destroy both enemy warships and submarines, it remains the primary offensive weapon carried by American attack submarines.
• Introduced in 1972, the torpedo has undergone several upgrades over the decades. Modern variants, including the Mk-48 ADCAP (Advanced Capability), feature improved guidance systems, electronics and propulsion.
• The weapon weighs around 3,800 pounds (about 1,700 kilograms) and carries a powerful warhead capable of crippling large naval vessels.
• The Mark-48 uses both active and passive sonar to track targets underwater, allowing it to home in on ships or submarines even if they attempt evasive manoeuvres.
• Unlike many conventional weapons, the torpedo is designed to detonate beneath a ship rather than striking its hull directly.
• When it explodes under the vessel, the warhead — roughly equivalent to 500 pounds of TNT, creates a massive bubble of gas. As the bubble expands and collapses, it snaps the ship’s keel, the central structural beam running along the bottom of the vessel.
• This so-called “keel-breaking” effect can tear a ship into two or more pieces, causing it to sink rapidly.
• The torpedo can travel at speeds of more than 55 knots (over 100 km/h) and can strike targets dozens of kilometres away, making it one of the most lethal underwater weapons in modern naval warfare.
• The Mark-48 is deployed on several classes of US submarines, including the Los Angeles-class, Seawolf-class and Virginia-class boats.

US defence secretary Pete Hegseth described the strike on the Iranian frigate as a “quiet death,” adding that it marks the first sinking of an enemy ship by a US torpedo since World War II.