If Prime Minister Sir Keir Starmer doesn’t increase spending on defence, he will have to lose 20,000 troops or both of our aircraft carriers. That’s the stark warning of Lord Robertson, who heads the Government’s Strategic Defence Review, according to sources.

His grim message comes at a tense time for international relations as Russia, China and Iran are all identified as major threats to our way of life.

It also coincides with president-elect Donald Trump about to take the helm of the most powerful nation in the world. And, as Trump has already made clear, Europe cannot expect a free ride on the coat-tails of US military power.

His attitude is correct, echoing that of former president Theodore Roosevelt who advocated a foreign policy of “speaking softly and carrying a big stick.”

Trump is no war-monger, doing everything he can to bring a resolution to international conflicts, but he does want the West to stand tall and strong. And that means pushing us all to make a fair contribution towards our own protection.

Dithering Keir must realise it is a good investment to ramp up defence spending to 2.5% along with our Nato allies. In fact, in anticipation of Trump, EU countries are already discussing raising their contribution from 2% to 3% of GDP. Significantly, Mark Rutte, secretary-general of Nato, hot-footed it to Florida to meet the president-elect, aware there needs to be a meaningful uplift in contributions.

And in his first speech as secretary-general this week, he warned the military alliance was not preparing for “long-term confrontation” with Russia. He said: “It is time to shift to a wartime mindset, and turbocharge our defence production and defence spending.”

As Starmer is always so keen to lead by example, he should promptly meet Nato’s raised shared target.

“Labour’s dithering on defence is a dereliction of duty that puts Britain’s security at grave risk,” former Defence Secretary Grant Shapps told Daily Express.

The failure to sufficiently ramp up British military spending in the 1930s, combined with appeasement, did little to dissuade Nazi leader Adolf Hitler from putting his nation on a war footing. By 1939, the RAF had only 488 light bombers and they were unable to even reach German targets, whereas the Luftwaffe boasted over three times as many bombers out of a total of 4,000 operational aircraft.

The good news is that Russian leader Vladimir Putin has clearly failed in his attempt to conquer Ukraine and may have to settle for a Trump negotiated peace. The ability of the Russian war machine has been found to be severely wanting, as has the regional ambitions of Iran, soundly thwarted by superior Israeli military technology and revolution in Syria.

It is valid to learn lessons from recent conflicts and make a shift in our own military expenditure, accordingly. Eye-wateringly costly aircraft carriers may make splendid status symbols but they are now increasingly vulnerable to ship-killing missiles. Drones make a far more effective and cheaper method of waging war, as does AI thanks to its capability of infiltrating foreign intelligence networks. More investment in this 21st century technology would also generate benefits in the civilian sector.

Shockingly, there are over 60,000 civil servants in the Ministry of Defence, that’s twice the number of service personnel in the Royal Navy or RAF, and just behind the 72,500 fully-trained soldiers in the British Army.

A reduction in pen-pushers might allow for more spending on frontline defences.

Above all, however, it is a strong economy that is the greatest deterrent. Soviet leader Mikhail Gorbachev knew the game was up in the Cold War when Reagan’s booming 1980s America had the resources to spend on its “Star Wars” anti-missile defences. With Trump rejecting net-zero impoverishment and advocating go-go capitalism, that is the best defence of all.

Economically faltering Britain, France and Germany must seek to copy that model, bringing wealth to the table, rather than weakening themselves in the face of Putin’s Russia with suicidal de-industrialisation.

Starmer should seize the moment to signal his commitment to Nato and match their increase in military expenditure. Not only will it put out the right message to our enemies, it will also demonstrate to our strongest ally that we are serious about helping to shoulder the burden of protecting democracy and freedom.

Starmer too frequently talks the talk, but this time he must walk the walk.