Prime minister Keir Starmer has commissioned a "root and branch" strategic defence review designed to equip the UK to "tackle international threats head on" and keep the nation "safe and secure".
Former New Labour defence secretary Lord George Robertson has been appointed to lead the review. Robertson led the Ministry of Defence from 1997 to 1999, during which time he oversaw a strategic defence review for the Blair government. He was secretary general of Nato from 1999 to 2003.
Launching the latest review, Starmer said Russia's invasion of Ukraine and the conflict in the Middle East underscored the extent to which the world had become "more dangerous and volatile".
He said the strategic review, which is due to report in the first half of 2025, would be part of the government's efforts to "forge a new clear-eyed approach" to the national defences.
"I promised the British people I would deliver the change needed to take our country forward, and I promised action not words," he said.
"We will make sure our hollowed-out armed forces are bolstered and respected, that defence spending is responsibly increased, and that our country has the capabilities needed to ensure the UK’s resilience for the long term."
Robertson's review panel includes UK-born foreign-policy expert Dr Fiona Hill, who is a former US presidential adviser, and former joint-forces commander Gen Sir Richard Barrons.
The panel will be overseen by defence secretary John Healey and supported by a defence review team of senior high-level experts from inside and outside government.
Between now and the end of September, submissions are being sought from serving and retired members of the armed forces, the defence industry, members of the public, academics, MPs, Nato members and other allies.
Healey said defence needed a "new era" because the current trajectory of depleted armed forces, procurement waste and neglected morale could not continue.
"Our armed forces need to be better ready to fight, more integrated and more innovative," he said.
"We need clearer accountability, faster delivery, less waste and better value for money. The review will ensure that defence is central to the future security of Britain and to its economic growth and prosperity.
"This new era requires a new type of review that moves at pace. The prime minister and I will therefore draw on both external military, industrial and foreign policy experts, and those from inside government, to help set the path for Britain’s defence for the next decade. Together, we will make Britain secure at home and strong abroad."
The MoD said the strategic defence review would aim to "put personnel across defence at the heart of future defence work"; strengthen UK homeland security; aid Ukraine in its fight against Russia; modernise the UK's nuclear deterrent; and adapt military services and equipment programmes to meet requirements.
As part of the announcement, both Starmer and Healey referred to the government's pledge to increase spending on defence to 2.5% of gross domestic product. However, the pledge lacks a timeframe for implementation.
Former national security adviser Mark Sedwill told BBC Radio 4's Today programme that it is vital for the UK to "consider the shape and capability" of its armed forces, rather than just the amount of money spent on them.
Lord Sedwill, who served as both NSA and cabinet secretary between April 2018 and September 2020, said simply increasing spending on defence to 2.5% of GDP would result in "plugging gaps" and "addressing shortfalls" in training, equipment, maintenance and ordinance. He said it would not deliver the kind of capabilities needed for defence and deterrence in the modern era.
"We have to modernise; we have to transform both our armed forces and – even more radically – the entire defence enterprise that supports them," he said. "And that's true of our European allies as well. Actually, more true for most of our European allies than it is for us. But we should lead the way with this defence review.
"A lot of this is about modernisation, transformation, improving the lethality, improving the capability, the readiness sustainment of our forces. This defence review really needs to get into that, and they need to be given the freedom to look at that in a transformative way."