Why is 2.5% UK's magic number when it comes to defence spending?

Rishi Sunak has promised to put Britain's defence industry "on a war footing" as he promised to boost defence spending to 2.5% of national income by 2030.

The plan to ramp up defence spending will be the biggest boost "in a generation" said The Telegraph. Speaking during a visit to Poland, the prime minister unveiled £75 billion in new funding that will take the defence budget to 2.5% of the UK's GDP – £87 billion a year – by 2030.

Sunak said the plan would make Britain "by far the largest defence power in Europe" and would serve to "show our enemies that we are resolute and determined". 

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The prime minister also committed to matching this year's £3 billion of military support sent to Ukraine every year until the end of the decade. 

The announcement comes after the US Congress finally approved a long-delayed $95 billion foreign aid package, with much of the package earmarked for Ukraine.

What did the commentators say?

As a member of Nato, the UK is already committed to spending 2% of its GDP on defence each year. But not all allied Nato member nations have hit this target in the wake of the 2007-8 financial crisis. 

In 2022, the UK was "one of just nine of Nato member countries to have met" the 2% target, spending 2.1% of GDP on defence, according to a 2023 UK defence expenditure briefing. 

Sunak has "essentially resurrected the same pledge Boris Johnson made a million years ago in 2022", as well as a hardening of earlier promises made by Sunak last year, noted London Playbook. 

But the plans will take spending "well above" Nato's 2% target and "pile pressure on European allies to follow suit" amid an ongoing "fierce transatlantic debate about defence spend in Europe", said Politico's Stefan Boscia. 

In February, Nato's secretary-general Jens Stoltenberg said that 18 member states were on track to meet spending targets, a figure he said was "a record number, and a six-fold increase from 2014, when only three allies met the target".

Defence sources told the BBC that the plans will allow the UK to build up its stockpiles of ammunition, such as artillery shells and missiles. "One lesson from the war in Ukraine is that most Nato nations would run out very quickly if they were involved in a war", said the broadcaster. 

Additional funding will also help resource Ministry of Defence programmes "already under way", such as an order for new frigates, the development of a new fighter jet, and the modernisation of Britain's nuclear weapons systems – all programmes that "are proving to be very expensive" with the Ministry of Defence "struggling to make ends meet on its existing resources".

Defence considerations aside, there is also "clearly a political dimension to this extra cash injection" as a general election looms, with Sunak already under pressure from some in the Conservative Party to increase defence spending ahead of the country going to the polls later this year.

But increasing the UK's defence budget to 2.5% of GDP may not be enough, argued Paul Mason in City AM. Russia is spending "40% of its state budget, and 6% of its GDP to rebuild its armed forces", he wrote. "That's not just to fund a new offensive in Ukraine, but to menace the UK and our Nato allies". 

Should the Nato-sceptic Donald Trump win the US presidential election in November and reduce the US's sizeable commitment to the alliance, "then 3% might be the minimum the UK needs to spend to hold things together in Europe," added Mason.

What next?

Sunak's defence spending plans have been welcomed by Nato, with Jens Stoltenberg praising the decision, saying that Britain was "leading the way" in Europe.

Officials said the defence boost would partly be funded by plans to reduce the size of the civil service, saving some £2.9 billion.