Britons need to be “think like troops” in the face of spiking tensions with Vladimir Putin’s Russia with the size of the regular armed forces dwindling, the head of the British Army will warn today.

With the number of soldiers having dropped below 76,000 – its smallest size in centuries – General Sir Patrick Sanders will outline his concerns when he addresses the International Armoured Vehicles expo in Twickenham.

He is expected to say the Government will need to begin calling men and women up to the armed forces to plug the gaps, according to The Daily Telegraph.

Gen Sir Patrick will stop short of calling for the introduction of conscription, but will use his speech to call for a “shift” in the mindset of ordinary people, where they think more like troops, and are mentally prepared for conflict with Russia.

It is not the first time Gen Sir Patrick, scheduled to step down as Chief of the General Staff in six months, has broached the subject of looming conflict.

Two years ago, after Putin’s invasion of Ukraine, he said the UK was facing its “1937 moment”, stressing the nation needed to prepare to “fight and win” in the face of Russia’s expansionist aims.

Putin is pushing forward in Ukraine after tripling military expenditure, and with Donald Trump targeting the November US Presidential election, the future of NATO military funding for Kyiv is far from guaranteed.

Congress is currently trying to pass a £79 billion package of aid in the face of opposition from Mr Trump’s Republicans.

Gen Sir Patrick’s remarks echo those of Admiral Rob Bauer, chairman of the NATO Military Committee, who earlier this week said nations needed be ready to “find more people if it comes to war”, and to consider “mobilisation, reservists or conscription”.

Adml Bauer further stressed his belief that the West needed to be “ready for all-out war in 20 years”. Boris Pistorius, Germany’s defence minister, went one step further this week, predicting war between Russia and NATO “within five to eight years”.

Also at the weekend, former chief of the general staff of the British Army warned the UK risked a repeat of the 1930s unless more was invested in its armed forces.

General Lord Dannatt hit out at the shrinking size of the army, which he said had fallen from 102,000 in 2006 to 74,000 today “and falling fast”.

He drew parallels with the 1930s when the “woeful” state of the UK’s armed forces failed to deter Hitler, saying there was “a serious danger of history repeating itself”.

Speaking on Sunday, Mr Shapps said spending on defence was currently below the target of 2.5 percent of gross domestic product (GDP), a measure of the size of the economy.

He told Sky’s Sunday Morning With Trevor Phillips: “We’re comfortably above two percent.

“But we are pledged to, when conditions allow, get to 2.5 percent.”

Challenged over when that goal would be hit, he told the BBC‘s Sunday With Laura Kuenssberg: “There is a trajectory upwards.

“I can’t give you the exact date because we’ve always said it’s as the economic conditions allow. But the point is we’re working to a plan.”

He also insisted the size of the army would not dip below 73,000 under the Tories, saying: “It’s not projected to go down to 50,000.

“It’s actually, specifically, to 73,000 plus the reserves.”

Also speaking on Sky News on Sunday, shadow home secretary Yvette Cooper refused to commit to Labour spending of three percent of GDP a year on defence if the party is elected.

She said: “Decisions for future spending if Labour wins the election would be for a Labour chancellor.

“But we have been clear about the importance of our national security.

“National security is the bedrock on which everything else in the country and everybody’s wellbeing is built and so of course that includes supporting our Armed Forces and making sure that they have the investment and the support that they need.”