I’m not certain who minted the phrase, but it is an excellent one to describe the decade or so that followed the fall of the Berlin Wall and the subsequent implosion of the Soviet Union. The affluent liberal democracies were treated to “a holiday from history”. The west started turning its Cold War swords into ploughshares once its principal ideological and military adversary had departed the scene. The collapse of the Soviet Union was followed by a dramatic decline in military spending. The UK, which was consuming 4-5% of its GDP on defence in the final stretch of the confrontation with the USSR, now devotes a smidgeon over 2% to securing the realm, sustaining its alliances and deterring its enemies. The bulk of this so-called “peace dividend” has been used to improve pensions and make health care better than it would have otherwise been. I hope you enjoyed it while it lasted. One strategic error was to fail to foresee that Russia could turn revanchist and menace Europe again. Another mistake common among western policymakers was to be beguiled by the theory that commerce and engagement with China would gradually lure Beijing to embrace democratic values. Vladimir Putin’s brutal war in Ukraine and Chinese designs on Taiwan are the main, but not the only, reasons that some shudder that there’s a 1937 feel about today, but this time with all the big powers armed with nuclear weapons. Even if you find that too apocalyptic, it is hard to dispute that our planet is looking more dangerously contested than it has done for a generation. One senior Tory remarks that we should be preparing to spend at least a decade in the shadow of “the threat of Russian aggression”. At the same time, it has become reckless to assume that the United States will always be there holding a protective umbrella over Europe. A hard rain is going to fall if Donald “I don’t give a shit about Nato” Trump gets back into the White House. Yet Britain has an army smaller than at any time since the Napoleonic wars, the Royal Navy is mothballing ships due to crew shortages, and the RAF lacks enough operational combat aircraft and is losing trained pilots faster than it can recruit replacements. Morale in all three services is low. One of the lessons of the bitterly attritional struggle for the freedom of Ukraine is that frontline troops are only as strong as the ability to keep them supplied with ammunition. Our arms manufacturing capability has at times struggled to replenish the weaponry sent in aid. Unless something is done, most Nato members will run out of munitions very quickly if they find themselves engaged in a significant conflict. So Rishi Sunak is right – not a phrase I or anyone else writes very often – when he says that the UK needs to become more serious about protecting its security and vital national interests. He is also right to call for the low-spending Nato members to start pulling their weight. About this, he and Sir Keir Starmer are in basic agreement. On a recent visit to Barrow-in-Furness, where nuclear submarines are built, the Labour leader said that “our nation’s defence must always come first”. He also performed a ritual that is demanded of Labour leaders before they are elected by saying that, if it came to it, he would not flinch from ordering the use of Britain’s nuclear arsenal. The contrast with Jeremy Corbyn is absolutely intended. One shadow cabinet member remarks: “In 2019, the hardest doors for Labour to knock on were those with Help For Heroes and British Legion stickers in the window.” In government, sources say that Labour would take a “Nato first” approach, on the grounds that it is the theatre where Britain has its most important treaty obligations and faces the most direct threats. Both the Tory and Labour leaders say that defence spending needs to rise to 2.5% of GDP. Neither offer any guarantees about when this will happen and both are avoiding having a frank conversation with voters about the price of security. The target date plucked out of the air by Mr Sunak is 2030. That is too little, too late for quite a lot of his own party and anyway pretty meaningless because virtually no one expects him to be resident in Number 10 in a year’s time, let alone six. Sir Keir says a government led by him will reach the target “as soon as resources allow”, a sometime-never kind of pledge. You can see why their rhetoric is much meatier than their commitments. Those wanting to see the UK putting more into defence face several challenges. The first is the lack of public enthusiasm for the idea. Sabre-swishing talk about the UK getting “on a war footing”, as the prime minister put it during a visit to Warsaw, has had little traction on public opinion so far. Sir Keir may declare that defence is “the number one issue for any government”, but it is far from the top priority for most of the electorate. In the most up-to-date ONS survey, voters placed international conflict a long way down the pecking order of the issues they believe to be the most pressing for the UK today. At eighth, it came in behind the cost of living, the NHS, the economy, the climate crisis, housing, crime and immigration. So one challenge for the politicians is to convince voters that the world has become as dangerous as they say it is. The public will also need persuading that bucks for bangs will be used wisely. This will be hard because the Ministry of Defence has such an atrocious record of repeated and costly procurement failures. The public accounts committee, in a report published last month, revealed a £16.9bn hole in the government’s defence equipment budget and concluded that the UK was in “an alarming place” because of the MoD’s “lack of a credible plan to deliver fully-funded military capability”. That followed an excoriating verdict from the Tory-chaired defence select committee that the “well and truly broken” procurement system has wasted billions of pounds. The UK’s two aircraft carriers were over budget and late to launch before becoming infamous for the regularity with which they break down. An even more notorious failure is the £5bn programme to modernise Britain’s aged and shrinking stock of armoured fighting vehicles. Bedevilled with design flaws and huge delays, the Ajax armoured vehicle was supposed to be in service in 2017. It still isn’t and won’t go on any operational deployment until 2026 at the earliest. It is no consolation, rather the opposite, that allies have been plagued with similar issues. If public opinion is to be rallied behind spending more on defence, voters will need convincing that they are going to get much better value for their money in future. Which brings us to the prickliest of the nettles that politicians hesitate to grasp. Where is the cash going to come from? Mr Sunak has been widely ridiculed for making pledges founded on fantasy financing. John Healey, the shadow defence secretary, was shrewd to ask why the promise to increase defence spending wasn’t in the recent budget so it could be independently scrutinised and properly costed. Labour says it will conduct a fresh strategic defence review within its first year in power. This is a sensible idea given how dramatically the threats have been evolving and escalating, but it is also a convenient refuge in which to hide from making hard commitments now. It is an exaggeration to say that we will have to choose between being a welfare state and a warfare state. The UK was both during the Cold War. It is true to say that if defence spending is going to rise, something else will have to give. Absent a miraculous surge in growth, the fundamental choice will be either higher taxes (at a time when many voters think they are being taxed quite enough already, thank you) or less in the kitty for public services and social support (at a time when most voters think we need to be spending more on them). Mr Sunak probably isn’t losing much sleep over that dilemma, because it is highly unlikely to be his problem for much longer. Sir Keir does have to worry about it, because this will almost certainly be landing in his lap like an unpinned hand grenade. To govern is to choose. To spend more on defence will mean choosing to spend less on things voters currently say they care about more. No one will call that a holiday. Andrew Rawnsley is the Chief Political Commentator of the Observer