Will a fraying American security guarantee lead some countries that once sheltered under Uncle Sam’s umbrella to start developing their own nuclear weapons?

The Financial Times has run a good piece on the possibility that a fraying American security guarantee will lead some of the countries that once sheltered under Uncle Sam’s nuclear umbrella to start developing their own nuclear weapons. The article’s authors quote Denis Healey, a significant (Labour) British politician for much of the second half of the 20th century, who was, at different times, defense minister and chancellor of the exchequer (finance minister). He had other roles besides.

Healey once said that U.S. nuclear policy required only “5 per cent credibility to deter the Russians, but 95 per cent to reassure the Europeans.” There’s something to that.

Europeans are not, at the moment, feeling reassured. To be sure, the U.K.’s nuclear guarantee, such as it is, already covers other NATO members, but Britannia’s umbrella is looking a little tatty.  Now President Macron is talking about extending France’s more formidable shield to other NATO members too, although this is far from a done deal, not least because it raises complex domestic political issues, which would not stay domestic.

For example, Germany’s likely new chancellor, Friedrich Merz, would prefer to team up with France. However, the French presidential election is due in 2027 and, for a mix of reasons, ranging from suspicion of Germany to fondness for Putin, neither Marine Le Pen’s RN nor France’s far left would, to Berlin, be reassuring guarantors. On the other hand, how would Poland (another potential new nuclear power, although cost and timing make that unlikely for now) react if Germany secured its own nuclear weapons? Europe cannot escape its history.

Best guess is that Germany would opt for “nuclear latency,” which, as explained in the FT article, means “putting the infrastructure in place to create a nuclear weapon if necessary without immediately building one.”

That may well be the approach taken by Japan, which, as a result of its peaceful use of nuclear power, and the opening of a nuclear enrichment plant a couple of decades ago, has enough plutonium stored domestically for “several thousand” bombs. According to unnamed U.S. experts cited by the FT, Japan could, given its industrial and scientific resources, (nuclear) arm itself “possibly within just a few months.” For obvious reasons, there are strong domestic political reasons (which I suspect would weigh more heavily than any constitutional objections) why Tokyo would not want to go down the nuclear path, just as there are obvious reasons why it would. Latency may be the compromise.

As for Seoul, there has long been popular support for a South Korean bomb (more, in fact than the FT article suggests) and it is likely to opt for nuclear latency sooner rather than later, although this may, to put it mildly, be complicated by North Korea, which already has nukes, and might opt for a preemptive strike if either Japan or South Korea went nuclear.

The contribution of the American nuclear deterrent to the success of the NATO alliance has been enormous, and its role too in the Pacific has been critical. While our allies should contribute more to their own defense than they have done (a process that is under way), it would be better if the rebalancing of existing arrangements (and the mood music that accompanies it) could be achieved without casting doubt on that ultimate American nuclear backstop.

And if the chance to pull that off has already passed, well . . .