This is an interesting notion that is unlikely to happen in anything but a very limited sense:
France has offered to create a joint UK-French nuclear deterrent by sharing submarine patrols, the Guardian has learned. Officials from both countries have discussed how a deterrence-sharing scheme might work but Britain has so far opposed the idea on the grounds that such pooling of sovereignty would be politically unacceptable.
In a speech this morning in London, Gordon Brown said he had agreed to further nuclear co-operation with France last week after talks with Nicolas Sarkozy. The prime minister did not comment explicitly about submarines, saying only that the UK and France would both retain “our independent nuclear deterrent”.
“We have talked about the idea of sharing continuity at sea as part of a larger discussion about sharing defence burdens,” a French official said.
A British official confirmed that the French government had raised the idea of shared “continuous at-sea deterrence”, but added that any such scheme would cause “outrage” in the midst of an election campaign.
Today, Brown said of his talks with the French president: “We have agreed a degree of co-operation that is, I think, greater than we have had previously but we will retain, as will France, our independent nuclear deterrent….
Sarkozy hinted at the potential for shared deterrence in a speech at Cherbourg. “Together with the United Kingdom, we have taken a major decision: it is our assessment that there can be no situation in which the vital interests of either of our two nations could be threatened without the vital interests of the other also being threatened,” he said.
Britain and France could synchronise nuclear deterrent patrols and co-operate in the deployment of surface fleet task forces, sources say. However, British officials played down the possibility of formal agreements on the nuclear deterrent – or on sharing each other’s aircraft carriers.
The idea of a shared deterrent is certainly interesting; during the Cold War, the NATO alliance essentially “shared” the nuclear umbrellas provided by the US, the UK, and France. Italy and West Germany did not need to invest in their own nuclear weapon programs because it was impossible to imagine an attack that would not also involve one of the three nuclear states. The current situation for France and the United Kingdom is very similar. While it’s obviously possible to imagine France or the UK going to war independent of one another, it’s difficult to envision scenarios where the nuclear deterrent of either country would become militarily relevant in an independent conflict. If anyone flings a nuke at either London or Paris, the expectation would be that the other would become involved (not to mention the United States). Thus, the idea of a shared deterrent has some appeal, especially given the high cost that both countries face in replacing their SSBN fleets.
That said, nuclear weapons play other roles besides deterrence. Nukes remain a prestige weapon, and in some sense guarantee a seat at the big power table. Without nukes, it would be much harder to distinguish France or the UK from the bevy of second tier powers (Germany, Italy, Japan, Poland, Spain, Canada) that lack nuclear weapons but have otherwise similar defense profiles. Indeed, it becomes very hard to justify the two security council seats for France and the UK if they’re sharing one of the key elements of their national power. Again, the idea of folding the two European permanent seats together (and replacing with, say, India or Japan or Brazil) makes some intuitive sense, but would be procedurally very difficult.
The command and control details of a shared deterrent would also be difficult to work out. There are a variety of different schemes, running from a CoG to CoG link (Brown calls Sarkozy from the ruins of London and asks him to shoot back at aggressor country X) to high level military contacts to the direct presence of French and British naval officers on each others submarines. Working out firing bureaucracy would be extremely complex, especially given that both countries seem to have somewhat idiosyncratic nuclear command procedures. Future procurement would also be a bit twitchy, as the RN SSBNs are scheduled for replacement prior to the French. However, the procurement issue might also be the firmest ground for collaboration; 4-5 boats to one design makes much more financial sense than 6-8 boats of two designs.