The Chilean Navy has officially joined the 2025 edition of the Diesel Electric Submarine Initiative (DESI), a multinational training exercise hosted by the U.S. Navy. On August 31, 2025, the submarine SS-20 Thomson arrived at Naval Base San Diego after a long voyage from its homeport in Talcahuano. Over the next five months, the vessel will operate under the U.S. Third Fleet, conducting advanced anti-submarine warfare (ASW) drills and enhancing interoperability in one of the Pacific’s most demanding training environments.
Commissioned in 1984, the Thomson remains a central asset in Chile’s undersea deterrence strategy. The diesel-electric attack submarine displaces 1,390 tons submerged, measures 59.5 meters in length, and can achieve submerged speeds of 21.5 knots. Armed with eight 533mm torpedo tubes, it is capable of multiple mission profiles, including anti-surface warfare, ASW, intelligence collection, and special forces insertion. Its low acoustic signature and modern sonar suite give it a tactical edge in contested waters.
A formal departure ceremony in Talcahuano highlighted the mission’s strategic importance, attended by Vice Admiral Raúl Zamorano, Chief of the Navy General Staff, and senior Submarine Force officers. Commander Gonzalo Álvarez leads the 45-person crew, which completed intensive technical and logistical preparations prior to deployment.
The DESI program, initiated by the U.S. Navy, addresses the operational challenge posed by diesel-electric submarines, whose stealth profiles make them difficult adversaries for nuclear submarines, surface combatants, and maritime patrol aircraft. Training will include ASW engagements, coordinated fleet maneuvers, NATO-standard rescue operations, and sea control missions, giving Chile a unique opportunity to refine tactics alongside a peer naval power.
Chile has participated in DESI since 2006, making this year’s involvement part of a nearly two-decade record of cooperation. The consistent participation has strengthened Chile’s submarine force readiness, supported regional stability, and reinforced multilateral naval partnerships in the Pacific.
The arrival of the Thomson in San Diego underscores Chile’s role as a reliable regional security partner and highlights the enduring value of diesel-electric submarines in modern ASW strategies. Beyond sharpening Chile’s deterrence posture, this engagement demonstrates Santiago’s commitment to interoperability and stability in the wider Pacific security architecture.
