Brazil Deploys Scorpène-Class Attack Submarine With U.S. Carrier Strike Group in Atlantic Drill.

Brazilian and U.S. naval forces conducted a high-end bilateral maritime exercise in the Atlantic Ocean on May 12–13, 2026, integrating the Brazilian Navy’s Riachuelo-class submarine Humaitá and frigate Defensora into the operating screen of the U.S. aircraft carrier USS Nimitz and destroyer USS Gridley. The drills demonstrated a level of tactical coordination significant for coalition naval warfare, as operating a foreign submarine close to a U.S. carrier strike group requires precise control of anti-submarine warfare, air defense, communications, and maneuvering inside a densely defended battlespace.

The exercise included anti-submarine warfare serials, formation maneuvering, communications checks, and air-defense training under Southern Seas 2026. Beyond interoperability, the engagement highlighted Brazil’s growing ability to operate advanced undersea and surface assets alongside a U.S. carrier force, reinforcing combined maritime deterrence and multinational readiness in contested Atlantic operations.

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Brazilian Navy Scorpène-class submarine Humaitá and frigate Defensora operate with USS Nimitz and USS Gridley in the Atlantic during Southern Seas 2026, testing carrier escort procedures, anti-submarine warfare coordination, air defense, and tactical interoperability between the Brazilian and U.S. navies (Picture source: U.S. Navy).

USS Nimitz provides the central operational problem for the engagement. A Nimitz-class aircraft carrier displaces about 100,000 tons at full load, is powered by two nuclear reactors, and can embark more than 60 aircraft depending on mission load. In Southern Seas 2026, Nimitz operates with Carrier Air Wing 17, including F/A-18E/F Super Hornet strike fighters, EA-18G Growler electronic attack aircraft, MH-60R/S Seahawk helicopters, and C-2A Greyhound logistics aircraft. This combination gives the carrier force long-range strike, airborne surveillance support, electronic attack, anti-submarine search capacity, and organic logistics. For Brazil, training near this kind of carrier group provides exposure to procedures that are rarely available in South Atlantic exercises.

The carrier itself is not defended by one weapon layer. Its close-in defenses are the last line, normally including Evolved Sea Sparrow Missiles, Rolling Airframe Missiles, Phalanx close-in weapon systems, and smaller-caliber guns for short-range threats. The more important point is how the force is organized around it: aircraft push the sensor and weapons envelope outward, helicopters search for submarines, escorts manage missile and air-defense coverage, and surface combatants maintain a moving screen against ships, aircraft, missiles, and submerged contacts. In practice, the carrier is protected by geometry, sensors, emissions control, aircraft, and disciplined escort positioning as much as by missiles.

USS Gridley carries the principal U.S. escort capability in this event. As an Arleigh Burke-class guided-missile destroyer, it is built around the Aegis Weapon System, AN/SPY-series radar, and Mk 41 Vertical Launching System cells that can employ Standard Missile interceptors, Evolved Sea Sparrow Missiles, Tomahawk cruise missiles, and Vertical Launch ASROC depending on loadout. The destroyer also carries a 5-inch Mk 45 naval gun, close-in defensive weapons, electronic warfare systems, and lightweight torpedoes. Its function in a carrier formation is concrete: build and maintain the recognized air and surface picture, assign engagement zones, protect the high-value unit from anti-ship missiles and aircraft, and contribute to anti-submarine prosecution when helicopters or sonar contacts require action.

BNS Humaitá introduces the most demanding tactical variable. The submarine is the second Brazilian Scorpène-derived Riachuelo-class boat delivered under PROSUB, Brazil’s submarine development program with French industrial support and construction at Itaguaí. Humaitá was commissioned in January 2024, following sea trials; the first boat, Riachuelo, entered service in 2022, with Tonelero and Angostura following in the program sequence. The class is reported at roughly 2,000 tons submerged, with a crew of about 32, six 533 mm torpedo tubes, and capacity for 18 weapons, including heavyweight torpedoes, anti-ship missiles, and mines.

For tactical purposes, a diesel-electric attack submarine is difficult to integrate near a carrier because its value depends partly on acoustic discretion and ambiguity, while the carrier force depends on positive control and rapid classification of underwater contacts. Humaitá can act as a training threat, a friendly undersea escort, or a deconflicted participant depending on the scenario. In each case, the exercise tests whether U.S. and Brazilian staff can exchange position data, define submarine operating areas, prevent fratricide, and coordinate helicopter search patterns without exposing sensitive submarine signatures.

Defensora brings a different but equally useful Brazilian contribution. The Niterói-class frigate entered Brazilian service during the Cold War and remains a multi-role escort after modernization. Defensora is listed at about 3,355 tons displacement, 129.2 meters in length, 13.5 meters in beam, a maximum speed of about 30 knots, a range of about 5,300 nautical miles, and an endurance of 45 days. Its modernized equipment includes air and surface search radars, fire-control radar, electronic support and countermeasure systems, a hull-mounted sonar, and the Brazilian SICONTA Mk 2 combat management system.

Its weapons fit remains relevant for escort training even if it does not match the missile density of a U.S. destroyer. Defensora is listed with a 114 mm Mk 8 naval gun for surface fire and limited naval gunfire support, Bofors 40 mm guns for close-range air and surface defense, an Albatros launcher for Aspide surface-to-air missiles, Exocet anti-ship missiles, Mk 46 lightweight torpedoes, anti-submarine rockets, decoy launchers, and a Super Lynx helicopter. In a combined formation, the frigate can screen a sector, prosecute submarine contacts with helicopter and lightweight torpedoes, maintain surface surveillance, and practice track-sharing with U.S. systems. This is the practical link between ship age and combat usefulness: an older frigate can still contribute if its sensors, helicopter, communications, and crew procedures are matched to a defined escort role.

The configuration matters because escorting an aircraft carrier is not ceremonial. A carrier force is a controlled tactical environment in which every ship’s position, radar emission, helicopter launch, sonar search, and weapon-control status affects the safety of the group. A submarine operating nearby adds further complexity because it requires water-space control, acoustic discipline, and agreed rules for identifying friendly and unknown contacts. When Brazil’s Humaitá and Defensora operate with Nimitz and Gridley, the exercise measures whether the two navies can move beyond basic interoperability into combined force protection around a high-value naval unit.

For the U.S. Navy, Southern Seas 2026 supports Fourth Fleet engagement objectives without requiring a permanent large-force presence in the South Atlantic. It gives U.S. crews experience with regional navies, regional operating conditions, and communications procedures outside the North Atlantic and Indo-Pacific focus areas. For Brazil, the event provides a test of submarine, frigate, and command-staff performance against a U.S. carrier operating model, while reinforcing Brazil’s role as the main South Atlantic navy with blue-water escort and undersea ambitions.

The military value of the engagement is therefore not in the photograph alone, but in the procedures behind it. Formation steaming confirms maneuvering discipline; communications drills expose incompatibilities before a crisis; anti-submarine warfare serials test sensors and command decisions; and air-defense training clarifies how a Brazilian frigate fits near a U.S. Aegis destroyer and aircraft carrier. The result is not an alliance guarantee or a new standing force, but a measurable improvement in familiarity, risk management, and tactical trust between two navies that share the same ocean and may need to coordinate there under less predictable conditions.

Written by Evan Lerouvillois, Defense Analyst.

Evan studied International Relations, and quickly specialized in defense and security. He is particularly interested in the influence of the defense sector on global geopolitics, and analyzes how technological innovations in defense, arms export contracts, and military strategies influence the international geopolitical scene.