Key Points and Summary – The 2009 Vanguard–Le Triomphant submarine bump showed how stealthy, passive, near-silent SSBNs can be invisible to each other—and how current “waterspace management” often excludes the very boats that most need it.
-With AUKUS and UK fleet growth adding more hulls, collision risk rises.
Vanguard-Class Submarine From Royal Navy. Image Credit: Royal Navy.
-The fix isn’t louder subs; it’s smarter deconfliction: ultra-classified, time-bound “keep-out boxes” shared bilaterally; depth/speed/route separation in choke points; scheduled transit windows; standard near-miss reporting; and a last-resort, low-probability-of-intercept safety ping reserved for imminent CPA.
-In short, privacy-preserving coordination that protects deterrence—and the crews—without giving away patrol patterns.
Is This How We Can Prevent Submarines from Crashing?
In February 2009, two of NATO’s most secretive nuclear-armed submarines – the British HMS Vanguard and the French Le Triomphant – collided deep beneath the Atlantic Ocean. Both submarines were on deterrent patrols, submerged, carrying ballistic missiles, and operating under stealth. The incident caused damage to both vessels but, thankfully, no injuries or radioactive leaks.
The collision, however, revealed how even allies – operating in darkness for security – can pose a risk to one another. And as more nuclear-powered submarines enter the world’s oceans – via the AUKUS deal among others – it’s hard not to wonder whether collisions like this are more likely to occur in the future, or if global powers have learned from this and other incidents like it.
Why the 2009 Crash Occurred
The 2009 collision occurred not as the result of a momentary lapse of judgement or one simple error, but a combination of factors that reveal how stealth technology can sometimes be used to the detriment of the vessels designed to use it. In 2009, both the French and British submarines were submerged and traveling at very low speeds, using only passive sonar – a system that detect sound from external sources without emitting any sound itself. Active sonar, does emit sound, would have revealed their positions and compromised their deterrent patrols.
Hull design also came into play. Both submarines were covered with anechoic tiles, which are designed to reduce the reflection of sonar – effectively making the vessels underwater equivalents of the B-2 Spirit stealth bomber, and other aircraft like it. Coupled with the vessel’s low speed, which means it emits minimal noise, detection of a submarine equipped with this technology is extremely difficult – even for similarly capable ships.
France SSBN. Image Credit: Creative Commons.
And if you thought NATO must have put in place mechanisms designed to ensure allied countries could more easily identify one another to avoid collisions like this, you’d be right. NATO has systems in place to allocate operation zones, known as “waterspace management,” designed to prevent collusions. However, ballistic missile submarines (SSBNs) are often excluded from being required to participate in shared reporting mechanisms to protect the secrecy of their patrol areas, making collisions more likely to occur.
Oceanographic effects and dynamics can also come into play, from thermoclines – layers of water where temperature changes rapidly with depth – to haloclines – zones where salinity shifts rapidly, creating density differences in the water.
These effects can disrupt sonar propagation, and under such conditions, even two modern SSBNs may not hear or detect each other until it’s too late.
The Risk Hasn’t Gone Away
The 2009 Vanguard-Le Triomphant collision was remarkable – and still a topic of discussion to this day – precisely because SSBN mishaps are rare and typically shrouded in secrecy when they occur. But recent developments show the conditions that enabled that collision are not confined to the past. In fact, the risk not only remains to this day, it could be argued that it is growing.
The first and perhaps most obvious reason is that more SSBNs are set to be deployed to the oceans. Under the Australia-U.K.-U.S. AUKUS pact, Australia is set to acquire three Virginia-class attack submarines from the United States in the early 2030s, with the option of up to five in total, if required. Those submarines are being purchased to fill an impending capability gap while the newer SSN-AUKUS design is also developed. Simultaneously, the United Kingdom and Australia are expected to co-build a fleet of SSN-AUKUS class submarines, with Australia aiming to deliver its first of that class by the early 2040s.
More submarines in the oceans means more opportunities for collision, unless more measures are taken to prevent them.
The United Kingdom’s commitment to scaling submarine production present a growing problem, too. In its 2025 Strategic Defence Review, the British government confirmed that it will build up to 12 SSN-AUKUS submarines, replacing its existing Astute-class SSNs beginning in the late 2030s. The U.K.’s fleet expansion includes large investments in industrial capacity to support continuous submarine production, indicating that this is a trend unlikely to disappear anytime soon.
Finally, there’s also the matter of operational practices. Though the submarines in development as part of the AUKUs deal are attack submarines (SSNs) and not ballistic submarines (SSBNs), they share several risky features: long submerged patrols, minimal use of active sonar, restricted communications, and stealth. All of these features make detection difficult, even among friendly forces.
Combine rising undersea congestion, with the number of submarines in active deployment increasing globally, and it’s hard not to see how this presents a problem. Though not every submarine will be carrying nuclear missiles, the threat to life persists amid a series of other major implications.
If another similar incident were to happen today, the stakes could be very high indeed.
A collision involving an SSBN could lead to reactor damage or leakage, credible escalation risk, or even an environmental disaster. Even an SSN-SNN or SSN-SSBN collision could be misinterpreted by others as aggression – and in tense geopolitical zones, those perceived acts of aggression could quickly escalate into something much more serious.
Beyond human risk, damage to any submarines involved in a collision could require long downtime, compromising deterrence postures, and costing billions in repairs.
Time for Information Sharing Measures?
New technology can only do so much to prevent collisions like this from happening in the future, with most new developments only making stealth better. The real question, with regards to how allied submarines can prevent these collisions, is what measures can be taken to ensures allies know how to minimize risk as much as possible.
The problem? Submarines rely on strict secrecy to maintain deterrence credibility. Vessels carrying ballistic missiles must remain invisible to guarantee a second-strike capability, which means avoiding active sonar, restricting communications, and withholding patrol zones from NATO’s waterspace management system. France, for example, has long declined to share positional data for its SSBN fleet, citing the risk of compromise.
But it was that very secrecy that raised the likelihood of a crash to begin with.
In 2025, on the verge of a substantial increase in deployed underwater vessels and amid growing global hostilities, might it therefore be time for allies to plan for limited information sharing?
About the Author:
Jack Buckby is a British author, counter-extremism researcher, and journalist based in New York who writes frequently for National Security Journal. Reporting on the U.K., Europe, and the U.S., he works to analyze and understand left-wing and right-wing radicalization, and reports on Western governments’ approaches to the pressing issues of today. His books and research papers explore these themes and propose pragmatic solutions to our increasingly polarized society. His latest book is The Truth Teller: RFK Jr. and the Case for a Post-Partisan Presidency.
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