Make no mistake: today’s Strategic Defence Review marks the start of British rearmament. Not only does it signal the UK’s commitment to increase defence spending to 3% of GDP, but to a type of spending designed to enhance the UK’s strategic clout in the world.

Alongside an ambitious plan to build up to 12 new attack submarines, and to create jobs in six new ammunition factories, one of the most striking commitments is to enter discussions with the USA aimed at “enhanced participation in Nato’s nuclear mission”. This innocuous sounding sentence represents a big change in nuclear posture. 

At present, only Belgium, Germany, Italy and the Netherlands host US-owned tactical nuclear bombs, with their aircraft designed to be “dual capable” of delivering such bombs on target. The UK, which lacks tactical nuclear weapons, could now volunteer to do likewise, but would need to buy a different variant of the F-35 combat aircraft than the one that is flown from the Royal Navy’s carriers.

That would be a major change in nuclear policy – because the British deterrent has, since the 1990s, been strategic-only. 

As I’ve argued here before, we need a wider range of options because Putin is now making regular threats to use nukes against Nato, and tactical nukes against Ukraine – so it makes sense to place more of Nato’s collective nuclear armoury closer to the front line, and distributed among a larger number of allies.

Over and above deterring Russian aggression, almost everything Labour has announced today looks designed to achieve three things: to boost Britain’s influence among its allies, to deliver high skilled jobs to places where they are scarce, and to get ahead of the game in the military technologies of the future.

These don’t only include drones – though the spectacular Ukrainian strike on Russia’s strategic bomber fleet on Sunday shows that we’ve hardly even begun to understand their power. 

The technological arms race is now focused on niche areas of science – like nanotech, materials and quantum computing – and Labour, to its credit, has understood that it in any conflict with Russia it is the science labs of Oxbridge, Imperial and Edinburgh, not the “playing fields of Eton”, that might be decisive.

For the armed forces, often bound by tradition and prone to inter-service rivalry, making the SDR work will be a challenge. Because in every domain of warfare – land, air, sea, space and cyberspace – they face the same problem: they are running decades-old kit designed for an era when Britain could choose which wars it fights, while at the same time moving to a completely new, digitally enabled way of fighting, in which technological change never stops.

In this context, faced with a Russia that has turned itself into a war economy, and itself learned to innovate rapidly – deterrence comes down to showing Putin that our own industry, science and digital technology base could crank itself up to speed, and indeed surpass what Russia itself could achieve.

For me, the most basic task of the SDR was to assess the scale of the Russian threat and offer the electorate an honest proposal of how to meet it – within our means.

Though it might sound simple to achieve, it was not achieved at any point during 14 years of Conservative government, above all after 2020, when Boris Johnson and Dominic Cummings declared a “tilt” of security priorities towards Asia, while systematically underfunding the ministry of defence.

Labour reversed that stance, declaring from day one that its priority is: “Nato First”. The SDR places maritime warfare as the highest priority and designates the Atlantic and the Arctic as the UK’s prime areas of interest.

There’s been a row today over the precise form of words Keir Starmer is using – describing the 3% target in the 2030s as an ambition. I think it’s clear that Labour means to find the money to achieve that – but it stands way outside the term of UK fiscal forecasting, and no chancellor would allow it to be stated as a firm commitment outside of a budget statement.

The real question with the SDR is: do the capabilities match the threats? The answer is: only if you believe Russia can be deterred through Nato remaining cohesive and the UK leading an enhancement of continent-wide nuclear deterrence.

If it cannot, then 3, 4 or even 5% won’t be enough. In 1939, after seven years of rearmament, Britain’s defence budget was 9% of GDP – and once war broke out it rose above 50%.

Today’s focus on the big stuff – submarines, which are the capital ships of the 21^st century, and a £15bn upgrade to nuclear warheads – reflects Starmer’s determination for this country to avoid any impression that it wants to be “Little Britain”. With a cash-strapped treasury, it is a decision to spend on what’s strategic, and rely on allies for that which is not.

There is even the promise, thinking long term, to specify within this parliament a replacement for the Dreadnought submarines, currently being built at Barrow: and they don’t even go out of service until 2050.

I would like to have seen more spending and faster – above all because defence industrial investment is one of the surest ways to boost growth and social cohesion in communities that have seen too little of it.

But until Labour can win the argument with the British people that they need to pay more tax, and tolerate more borrowing to fund defence, progress is going to be incremental. That, in turn, will depend on the outcome of Ukraine’s peace negotiations with Russia. If they fail – and that looks likely – people may wake up to the fact that the prospect of endless war on our doorstep requires a change of attitude to defence. In that sense, the SDR was the start, not the end, of something.