The Portuguese Navy’s REPMUS 26 exercise at the Tróia peninsula, south of Setúbal, ends today, 25 September, after almost four weeks of testing uncrewed ships, submarines and aircraft. This year the Nordic countries did something they had not done at Tróia before: they formed their own command element, a task group called “Valhalla”, and put their national forces and their companies under it.
The Finnish Defence Forces’ magazine Ruotuväki reported that the joint Nordic structure caught the attention of other participants. “Other participants have been amazed at the level of cooperation and cohesion the Nordic countries can achieve together,” said Commander Janne Vihervaara (quotes from Finnish and Swedish sources are NorthSouth HQ translations), who added that Nordic cooperation had “significantly” improved the cost-effectiveness of taking part.
The biggest drone test range in the world, run from Portugal
REPMUS — Robotic Experimentation and Prototyping with Maritime Uncrewed Systems — is organised by the Portuguese Navy with the Faculty of Engineering of the University of Porto (FEUP), NATO’s Centre for Maritime Research and Experimentation, NATO’s maritime uncrewed systems capability group and the European Defence Agency. It started on 31 August at the Navy’s Operational Experimentation Centre in Tróia.
The Navy said on 22 September that the 16th edition brought together more than 3,700 people from 36 navies, more than 130 research and development companies, 13 universities and about 300 uncrewed systems, supported by 14 ships. Figures presented the same day to President António José Seguro, and reported by Observador, were higher: 4,445 registered participants, about two-thirds civilian, and 575 different systems under test, with the Portuguese Navy bringing 45 system configurations, industry 51 and academia 11. The Navy’s chief of staff, Admiral Jorge Nobre de Sousa, said Portugal is helping draft NATO STANAG 4817, the standard meant to let uncrewed systems from different makers plug into the same command-and-control networks.
Sweden: 300 people and 28 systems
Sweden gave the most detailed public account of its contribution. The Swedish Armed Forces said on 24 September that more than 300 people from the armed forces, companies and other agencies took part, with 28 craft and systems: aerial drones, surface and underwater vehicles, and an uncrewed version of the Stridsbåt 90 combat boat. Sweden played on the opposing “B side” in a combined force with the other Nordic countries and Ukraine.
“The systems we operate here, we don’t have at home,” said Robert Sandgren, head of the Swedish delegation and a technical officer at the Swedish Defence Materiel Administration (FMV). The navy’s priorities, according to development officer Magnus Lind, are maritime surveillance, anti-submarine warfare, mine clearance and counter-drone capability. Company technicians were on site so that craft could be modified during the exercise.
Finland: radios without satellites, and an airship
Finland focused on operating when mobile networks and satellite links are denied. It brought a cognitive HF radio system for long-range links without fixed infrastructure, and the Turku University of Applied Sciences provided an uncrewed surface vessel as a test platform.
The most visible Finnish system was commercial. Kelluu, the Finnish maker of hydrogen-lifted uncrewed airships, flew two 12-metre airships at Tróia carrying a Trillium sensor and an IMSAR synthetic-aperture radar. Janes reported that Kelluu, which flew for the “blue” side in 2025, operated this year as an adversary under the Valhalla unit. At a briefing on 21 September the company announced a second-generation airship that triples endurance to 36 hours, and a new factory in Finland for fleet production, which it said could be replicated in other allied countries.
Why this matters for the corridor
REPMUS has become one of the places where Nordic navies and defence companies test and buy uncrewed systems, and it is run from Portugal. For Portuguese suppliers the Nordic task group is a buyer list in one place: the Swedish, Finnish and other Nordic delegations spent four weeks next to Portuguese companies such as Beyond Vision, whose drones were shown to the President. For Nordic companies, Tróia offers something they cannot easily get at home — large-scale live testing with 36 navies — and a way into the Portuguese Navy, which is modernising and co-writing the NATO interoperability standard. The Nordic “Valhalla” format is likely to return for REPMUS 27.