Some veterans will be mobilised as part of a major exercise next year testing the UK’s resilience for war.

The government exercise will challenge the Ministry of Defence (MoD) “on a scale that we haven’t seen for a very long time” on its reaction in the event of a conflict, armed forces minister Louise Sandher-Jones said.

The drill will involve an as-yet unspecified number of the British military’s strategic reserve, which has an estimated 95,000 retired regular and reserve officers.

It forms part of a plan by the MoD for a “real step change” to use the strategic reserve more, following warnings of a workforce retention crisis.

Sandher-Jones is herself part of the strategic reserve, having previously served in the British Army as an intelligence officer before becoming an MP.

“Certainly when I left the Army and found out I was in the strategic reserve, I just filed it away and never thought about it again,” she told the House of Lords national resilience committee on Monday.

“We are definitely no longer in that space – the strategic reserve is a real commitment for those who are in it, and they will be exercised as part of our exercise programme next year.”

The exercise in 2027 will “go through measures to call out, to use and equip” procedures to mobilise retired troops at scale should it ever be needed, she added.

It comes after the chief of the defence staff, Air Chief Marshal Sir Richard Knighton, warned in January there was not an effective system of engaging them.

Earlier this year, ministers raised the age limit for the strategic reserve – which includes the Army, Navy and Royal Air Force – from 55 to 65 and lowered the threshold for them being called into service.

The government is under pressure to raise defence spending to 3% of gross domestic product (GDP) by the end of the decade, up from an estimated 2.4% last year, according to Nato figures.

A major government awareness campaign will also take place in the coming months to make the public more prepared for emergencies.

Briefings have suggested this could include stockpiling tinned food and bottled water in the event of extreme weather and cyber attacks.

Sandher-Jones praised Finland for “showing the way ahead” with Europe’s largest civil defence exercise since World War Two, which saw more than 2,000 people take part in an underground sports hall earlier this week.

She also said young people would prove essential to the military’s readiness for future threats.

She hinted a new military “gap year” for under-25s, announced in December and now recruiting its first 150 students until March 2027, could be scaled up faster if it proves successful.

She added that the military “has a role in combatting Neets”, the official term for the one in eight young people in the UK who are not in education, employment or training, by expanding cadets in schools.

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