Security at French nuclear submarine base fires at unidentified drones

France’s Ministry of the Armed Forces is investigating the overflight of unidentified drones above the Île Longue naval base in western France, the home port of the country’s nuclear-armed ballistic-missile submarines.  

The incident occurred on December 4, 2025, around 19:30 local time, according to reporting by FranceInfo. 

Five drones detected over a key strategic site 

Security personnel at Île Longue detected five drones flying over the installation, prompting an immediate activation of counter-drone procedures. Fusiliers marins stationed at the base opened fire as part of the response protocol. A search operation was launched to locate any debris or remnants of the devices, though French authorities have not confirmed whether any drones were neutralized. 

The French Ministry of the Armed Forces has not yet provided further details and has not attributed the incident to any actor. As of publication, the origin and type of drones involved are unclear. No group or individual has claimed responsibility. 

A central pillar of French nuclear deterrence 

Located in the Bay of Brest, Île Longue is the operational base for the French Navy’s fleet of ballistic-missile submarines, which carry the country’s sea-based nuclear deterrent. The site hosts maintenance facilities, missile storage areas, and berthing for the four Triomphant-class submarines. 

Because of its strategic role, the base is among the most heavily secured military installations in France. Drone overflights have been reported before, including a similar episode in January 2015. 

Rising drone activity around sensitive sites 

The incident comes amid a broader uptick in drone-related intrusions near military, nuclear, and governmental sites across Europe. While many cases involve small, commercially available devices, their presence above critical infrastructure raises concerns about espionage, surveillance, or attempts to probe security responses.  

On December 1, 2025, up to five large drones were detected by an Irish navy ship near the flight path of Ukrainian President Volodymyr Zelenskyy during his arrival in Dublin for a state visit.