On September 13, 2026, the Royal Navy's experimental Extra Large Uncrewed Underwater Vehicle (XLUUV) EXCALIBUR successfully launched a US Navy MK-48 MOD 7 Common Broadband Advanced Sonar System (CBASS) heavyweight torpedo. The test took place at the British Underwater Test & Evaluation Centre (BUTEC) in the Inner Sound, northwestern Scotland.

The event was aimed at validating the mechanical, electrical, and software integration of a kinetic payload such as the MK-48 on a large unmanned underwater vehicle. Conducted under Project BROADSWORD (Royal Navy) and TRIAL IRON (US Navy), it marked a significant operational milestone for Pillar 2 of the AUKUS initiative.

Admiral Daryl Caudle, US Navy Chief of Naval Operations, described the test as a historic first for undersea operations between allied navies and the realization of a shared vision for effective naval interoperability. Vice Admiral Rob Gaucher, head of US submarine programs, highlighted the project as a critical step forward in enhancing the lethality of unmanned platforms in the undersea domain.

Developed under Project CETUS by the British Submarine Delivery Agency, EXCALIBUR is 12 m long and displaces approximately 19 t. Delivered to the Royal Navy in May 2025, it capped a 3-year development effort that included 2 years of sea trials. These culminated in the TALISMAN SABRE exercise held in Australia in August 2025, during which EXCALIBUR was remotely piloted in British waters from an operations center located in Australia — another event carried out under AUKUS Pillar 2. Pillar 2 encompasses at least 8 working groups: 6 focused on capability areas — undersea capabilities, quantum technologies, artificial intelligence and autonomy, advanced cyber capabilities, electronic warfare, and hypersonic and counter-hypersonic capabilities — and 2 devoted to innovation and information sharing.

Project BROADSWORD was approved in February 2026 by the US Navy's Department of the Navy Rapid Capabilities Office (DONRCO) and completed in less than 7 months through close cooperation with the Royal Navy, the Pentagon's Defense Innovation Unit, the Naval Undersea Warfare Center Keyport, and industrial partners. It was co-managed with the Portfolio Manager for Robotic and Autonomous Systems, a newly established position responsible for US Navy surface and underwater drone procurement.

Building on this success, the US Navy and international partners will continue accelerated development through Project CUTLASS, employing Anduril's DIVE-XL drone — selected under the Combat Autonomous Maritime Platform (CAMP) project and conceptually similar to EXCALIBUR — to refine the integration of more sophisticated payloads on XLUUVs, command and control architectures, and tactical employment scenarios. These activities fall within the broader framework of AUKUS Pillar 2, with deliveries of vehicles and enabling materiel starting in 2027. Objectives include protecting critical underwater infrastructure and conducting operations in undersea surveillance, anti-ship warfare, electronic warfare, mine countermeasures, and maneuver in non-permissive littoral environments.

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