Air Chief Marshal Sir Richard Knighton, the Chief of Defence Staff, said it was important for society to “understand the stakes” of maintaining the country’s safety.
The comments came on the eve of Remembrance Sunday in Britain.
Conservative leader Kemi Badenoch echoed Sir Richard’s comments, calling it “tragic and concerning” that many people no longer felt the call to serve their country.
Sir Richard, who took over as Chief of the Defence Staff in September, warned of an “increasingly uncertain world”.
The Air Chief Marshal is responsible for delivering the strategic defence review published in June which comes alongside the Government’s aim to boost defence spending to 2.5% of GDP by April 2027.
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Referencing Russia’s invasion of Ukraine to argue that European countries were not as safe as they once were, he said: “This conflict reminds us that peace is never guaranteed. It (the UK) must be defended, and sometimes at great cost.
“Whether deterring aggression on Nato’s eastern flank, supporting hurricane relief efforts in the Caribbean, or protecting critical undersea cables at home, we can be proud of our armed forces and what they do for the nation.
“But defence is not the responsibility of the military alone. It is a national endeavour. It requires investment, innovation, and the support of a society that understands the stakes.”
Considerable cuts over throughout the decades have led to Britain’s military shrinking, with the 70,000-strong regular Army now at its smallest size since the Napoleonic war.
Following the war in Ukraine, calls to rearm have been sharpened, however, with defence chiefs now seeking to make Britain’s military “more lethal” than ever, while the Government pumps billions of pounds more into the forces.
Mrs Badenoch, leader of the opposition, has reinforced the calls from Sir Richard, saying Britain is “losing a sense of who we are and what we’re fighting for”.
She credited the “slow erosion of pride in our schools, our institutions, even parts of our media where the story of Britain is too often told through shame” as affecting national morale, saying only 10% of those aged between 18 and 28 would be prepared to go to war for the country.
She added: “A nation is only a nation when people are prepared to defend it. And it is both tragic and concerning that many people in Britain today no longer feel that call.
“Why would young people want to fight for their country, when they are told that where they come from is wicked? That their inheritance is racist.
“How many people now, when they think about Britain, picture this as the country that stood alone against Hitler, led the fight against Soviet tyranny and has a longer history of stability and democracy than any other major power.
“This is the country that spent a fortune to end slavery in the world. Our history is something to be proud of. The wars we remember were not won by Britain alone, but by Commonwealth troops across national and ethnic divides fighting side by side to defend liberty and democracy.
“We are told again and again that diversity is our strength, when in reality the opposite is true. It is putting our differences aside and standing behind a shared national story that makes us stronger.”
