Defending the realm is supposed to be a prime minister's first priority. Yet Sir Keir Starmer is accused by two departing defence ministers of failing to provide the means to meet that vital aim.
So who is right? Is the government not doing enough to keep us safe? Or is this merely a Whitehall spending row that has gone catastrophically wrong?
The government currently allocates about £66bn for defence. That supports the UK's armed forces which remain highly regarded by friend and foe alike.
The money also pays for the nuclear deterrent. The UK is surrounded by water and has strong allies. All of these factors contribute to keeping us safe.
But successive governments have struggled to get a grip on defence spending. They spent less after the Cold War ended and failed to spend more as the world became more dangerous. As a result, the army, navy and air force contracted.
To its many critics, the Ministry of Defence failed to spend well what money it got, botching procurement after procurement, delivering new equipment late and over budget. Whitehall often failed to resolve its internal tensions, both No 10 and Cabinet Office unable - or too weak - to manage repeated rows between Treasury and MOD.
What is different about this row is its context. The world is changing fast. The nature of the threat against the UK is changing. Less immediate concern about non-state actors and militant groups such as al-Qaeda or ISIS. More focus instead on state-on-state aggression such as from Russia and Iran.
That threat is increasing. In his letter replying to John Healey's resignation, the prime minister wrote: "The world today is more dangerous and uncertain than at any point in our lifetimes".
The nature of warfare is also changing. Less need, perhaps, for traditional armour and ships. More focus on drones, cyber, space and technology as the wars in Ukraine and the Gulf have shown. What matters is the mass production of cheap and lethal projectiles that are adapted in real time, not long-term investment in big and vulnerable platforms that become outdated fast.
And all this is happening at a time when the United States has made it clear that it is no longer prepared to subsidise the defence of its European allies, demanding they finally meet their Nato spending targets.
These factors have made the need to spend more on defence more pressing. In response, the government made bold promises. The UK spent 2.3% of gross domestic product – or national output – on defence last year. Labour says that will rise to 2.5% by next year. And then, it promised to increase spending further, along with other Nato allies, to 3.5% of GDP by 2035. At the Munich security conference in February, the prime minister pledged: "We are going to have to spend more faster".
The government has also been ambitious in the commitments it has promised allies: to deploy land forces to Ukraine after a future ceasefire; to lead a multinational force protecting the Strait of Hormuz if the fighting ends; to provide Nato with a strategic reserve corps; to lead the alliance's defence of the High North and Arctic.
The accusation against Sir Keir Starmer and Rachel Reeves, the chancellor, is that they were and are not willing to find the money to meet these targets and commitments. Justin Crump, CEO of the Sibylline risk intelligence firm, told Forces News: "The government is not prepared to put its money where its mouth has been."
The delayed "defence investment plan" was supposed to deliver the money to meet the shopping list set out in last year's "strategic defence review". But earlier this year, the defence chiefs warned ministers they needed an additional £28bn over the next four years simply to meet existing commitments. This infuriated No 10 and the Treasury which had believed the SDR commitments could be fully funded by existing budgets.
Since then, a furious Whitehall battle saw that number reduced first to £18bn. Now it has reportedly settled somewhere around £13bn. Healey resigned because he did not think that was enough. As he wrote to the PM: "I am being forced to make decisions that would reduce the readiness of our Forces and increase the risk to personnel on operations, and could make the country less safe."
To get a sense of the shortfall, consider this: the Treasury is currently thinking of giving the MOD an extra £13bn or so over the next four years. Bee Boileau, a research economist at the Institute for Fiscal Studies, told me recently that that was what would be needed every year for the government to meet its 3.5% GDP target in 2035.
Last week the prime minister said publicly that UK intelligence believed "there could be an attack by Russia on Nato as soon as 2030". One senor defence figure told me that if that were true, "then we should be doubling spending".
So in the absence of a defence investment plan, huge uncertainty remains. Defence firms are struggling, some even going bust, because contracts have been repeatedly put on hold.
Each of the three services face uncertainty over what weapons, equipment and resources they may get. The modernisation of the nuclear deterrent, with new submarines and warheads, may be protected. So too may be plans for new attack submarines via the Aukus partnership with the US and Australia.
But will the army get a full roll out of its new AI digital targeting system? Will it have to temper its orders of the long-delayed and ill-fated Ajax armoured fighting vehicle? Will the navy get its hybrid fleet of uncrewed ships? Will its programme to renew its frigates face further delays? Will the RAF get as many 6th generation fighter jets as it wants? Will it have to cut orders for F35 warplanes? Will the services be able to restock their arsenals of missiles and munitions, much of which have been given to Ukraine?
And crucially, will the armed forces get what they need for future wars? In his resignation letter, Al Carns said: "We are still purchasing capability suitable for the last war while our adversaries arm for the next one." In particular, will the military get the drones and integrated air defence systems they need to defend the UK's skies from the kind of threat experienced not just by Ukraine but also the Gulf?
A decision of some sort is needed soon to avoid further damage to Britain's reputation overseas. Next week new Defence Secretary Dan Jarvis will meet his Nato counterparts in Brussels. They will want to know what he plans to do to resolve this crisis. They know the UK is slipping down the alliance's spending targets. They also know the UK is, according to defence insiders, almost at the bottom of the Nato leaderboard for meeting its capability targets.
Next month, at a summit in Turkey, the prime minister will himself have to face fellow Nato leaders, including Donald Trump, and set out what money he is prepared to spend on defence. They may be hard conversations.
