The Integrated Review, known by its full title of Integrated Security, Defence and Foreign Policy Review, was first announced by Boris Johnson in December 2019.
The aim of the review is to cover "all aspects of international policy from defence to diplomacy and development", with the Prime Minister describing it as the "biggest review of our foreign, defence, security and development policy since the end of the Cold War".
Its first phase has taken place, with the announcement of £16.5 billion extra funding for the Ministry of Defence.
The Integrated Review's findings had been expected to be published by the end of 2020, although in October the Government said it was considering the future of the Integrated Review, following confirmation that a separate Treasury spending review would cover only one year, instead of three.
The final conclusions of the Integrated Review are now due to be unveiled next year, according to the Prime Minister.
What is the Integrated Review?
The review was launched in February.
Boris Johnson told Parliament that "by transforming this country's economy and by raising productivity, we will ensure that defence and security are amply provided for".
Downing Street has previously said the Integrated Review will go beyond the parameters of a traditional strategic defence and security review (SDSR) by looking at the "totality of opportunities and challenges" the UK faces.
The aim is for British military chiefs to use the review to reshape the Armed Forces, with decisions made according to threats facing the country, with it also looking at developing defence capabilities and procurement.
Defence, foreign and security policy, threats of the next decade, relationships with allies and changing strategy on the international stage will also all be examined.
Watch: The Defence Secretary and the Chief of the Defence staff both spoke about the Integrated Review during a briefing in September.
After being temporarily paused in April due to the coronavirus pandemic, the review resumed in June 2020, with the Government inviting submissions of evidence in September.
During a briefing last month, Ben Wallace warned the UK's enemies have "studied our vulnerabilities and adapted far more quickly than us", adding that the review will "represent a step-change – not just in how we adapt to the threat, but in how Whitehall faces up to the difficult decisions that must be made".
"In the past, too many reviews were over-ambitious or underfunded or both," he continued.
"Too often the budget, not the threat, did the talking. So we will pivot away from what we have become used to and instead reshape our Armed Forces to become a force fit for tomorrow’s battles, not fighting yesterday's."
Tobias Ellwood, the chair of the Defence Committee, told Forces News earlier this year the review could provide the Ministry of Defence with the chance to "press that reset button".
"We've actually had six reviews since 2010, and for different reasons, they didn’t work," Mr Ellwood said.
"They were too close to a spending review at the same time, or they were curtailed by timing.
"This is a huge endeavour by the Government and we do have to get it right.
"Understanding what our defence structure is at the moment, understanding the threats - then asking that very difficult question: what do we want to achieve on the international stage?"
Mr Ellwood then told the BFBS Sitrep podcast last month the review should not be conducted by "telling people to start saving money".
He continued: "We have a fantastic Armed Forces, they're extremely professional but they are over-stretched.
"The Air Force, the Army, the Navy – we ask them to do an awful lot. I hope this Integrated Review will firstly recognise that, but also conduct things in a sensible, chronological order."
The current practice of undertaking a strategic defence and security review (SDSR) every five years dates back to 2010.
The most recent SDSR was published a few months after the 2015 election.
Recommendations from the review are expected to be implemented over a period of several years.