Britain and Germany’s highest ranking military chiefs have made an unprecedented joint appeal to the public to accept the “moral” case for rearmament and prepare for the threat of war with Russia.

The pair said they were making the plea not just as the military leaders of two of Europe’s largest military spenders, but “as voices for a Europe that must now confront uncomfortable truths about its security”.

Air Chief Marshal Sir Richard Knighton, UK chief of the defence staff, and Gen Carsten Breuer, German Chief of Defence said Russia’s military stance had “shifted decisively westward” and a “step change” was needed in Europe’s defence and security.

In a joint article published in the Guardian and the German newspaper, Die Welt, in the wake of the Munich Security Conference, the soldiers said they had a duty “to explain what is at stake so that the public could understand why the UK and Germany have committed to the biggest sustained increases in defence spending since the end of the cold war”.

“There is a moral dimension to this endeavour. Rearmament is not warmongering; it is the responsible action of nations determined to protect their people and preserve peace,” they write.

There is significant reluctance among voters in Britain and Germany to accept economic pain in return for rearmament, even while majorities in both countries believe the outbreak of a third world war is more likely than not in the next five years.

In Britain, fresh polling by YouGov found that a minority favour tax rises (25%) or spending cuts (24%) to fund greater spending on the armed forces – including those who say it is very important to increase UK hard power.

The German and French publics are also now less likely than they were last year to support increased defence budgets if it meant a trade-off with other investment, according to a poll for Politico this month.

The UK prime minister, Keir Starmer, said at the weekend that there was an urgent need for a closer UK defence relationship with Europe, covering procurement and manufacturing, so that the UK would be at the centre of a stronger European defence setup.

In a visit to the Munich Security Conference, he told the audience: “We are not the Britain of the Brexit years” as he argued that the long-term threat posed by Russia and the need for Europe to take greater responsibility for its own defence required the UK to integrate more closely on defence procurement with European allies.

Europe was, he said, “a sleeping giant” but there had been fragmented industrial planning and procurement

Knighton and Breuer write: “If Russia perceives Europe as weak or divided, it may be emboldened to extend its aggression beyond Ukraine. History teaches us that deterrence fails when adversaries sense disunity and weakness. We know that Russian aggression and intentions extend beyond Ukraine.”

Echoing language used by government figures in Britain, Germany and other European states, Knighton and Breuer said the complexity of threats demanded a “an honest continent-wide conversation with our publics that defence cannot be the preserve of uniformed personnel alone”.

They called for a “whole-of-society defence” with resilient infrastructure, research and development in technology from the private sector, and national institutions prepared to function under increasing threats.

The UK and Germany have committed to deepending security and defence cooperation and signed what became known as the Trinity House Agreement in 2024.

The German government is under pressure to meet its promise to revive economic growth after a prolonged downturn and to ramp up defence spending amid concerns over Russian aggression.

Germany is permanently stationing a combat brigade of 4,000-5,000 troops to Nato’s eastern flank and has amended its constitution to make essentially unrestricted funding available for defence.

Procurement of several thousand armoured vehicles has also started, alongside an expansion of industrial capacity. Britain is meanwhile building up to six munitions factories, which are aimed at generating what the Ministry of Defence describes as an “always on” capability to sustain munitions stockpiles.

The debate about European security – three years after Vladimir Putin’s full-scale invasion of Ukraine, and amid increasing ambiguity around the extent of US support for Nato after Donald Trump’s return to the White House – comes as both governments in Germany and the UK seek to rebalance spending after an era of investing a supposed “peace dividend” in public services.

Nato leaders at last year’s Hague summit committed to spending 5% of GDP on defence and security by 2035.

Such a move would expand the British economy in the short term, according to research, but there is still opposition on the left of the Labour party to defence hikes at the cost of spending on health and alleviating poverty. That debate is even more polarised in Germany, with opposition to increased defence spending on the left and, to a degree, from the surging far-right AdF party.

Speaking on the opening day of the Munich conference, Germany’s chancellor, Friedrich Merz, singled out the threat Russia posed to Europe, warning “freedom can no longer be taken for granted”.

“We have to understand that in the era of big powers, our freedom is no longer a given. It is at stake. We will need to show firmness and determination to assert this freedom,” he said.

Merz also disclosed he had held initial talks with the French president, Emmanuel Macron, over the possibility of joining France’s nuclear umbrella, underlining his call for Europe to develop a stronger self-standing security strategy.