The Integrated Review into the future of the UK's foreign, defence and security policy has been published.
The 100-page-plus document has been billed as the most radical reassessment of Britain's place in the world since the end of the Cold War.
On 22 March, the Defence Command Paper will be published, and is expected to contain further details about the future of defence.
Here are the key points for defence in the Integrated Review Of Security, Defence, Development and Foreign Policy
The review commits to Britain deploying "more of our Armed Forces overseas more often and for longer periods of time" for training and exercises.
The Prime Minister announced in November a £16.5bn increase in defence spending over the next four years, focusing on the future battlefields of space and cyber.
Regarding hardware, the newly-published report mentions a "new Multi-Role Ocean Surveillance Ship" for the Royal Navy, plus a pledge for the UK to have "at least 48 F-35s by 2025".
Mr Johnson, speaking in the Commons about Scotland, said: "There'll be further investments in Lossiemouth," and confirmed there will be "no threat, for instance, to the Black Watch".
In response to a question about how the military will be reduced by 10,000 personnel, the Prime Minister stated: "There'll be no redundancies across the Armed Forces."
Boris Johnson later said: "The Army, including reserves... will be over 100,000.
"But it is the duty of this Government to take the tough decisions that are necessary to modernise our Armed Forces, as well," he added.
Watch: What is the Integrated Review?
The Integrated Review commits to increasing the number of nuclear warheads Britain has at its disposal for its Trident missiles to 260, reversing a move to reduce the stockpile to 180.
The review says a "minimum, credible, independent nuclear deterrent" remains "essential in order to guarantee our security".
But ministers have concluded that with a "developing range of technological and doctrinal threats", it is not the time to press on with 2010 plans to lower the overall stockpile of nuclear warheads but increase them to "no more than" 260.
The report also says there is a "realistic possibility" that a terrorist group will launch a successful chemical, biological, radiological or nuclear attack by 2030.
In a "tilt" in strategic direction and diplomacy, the UK will look to become a bigger player in the Indo-Pacific, reflecting the region's "growing importance".
"By 2030, it is likely that the world will have moved further towards multipolarity, with the geopolitical and economic centre of gravity moving eastward towards the Indo-Pacific," the document says.
The shift will be underlined by the deployment of HMS Queen Elizabeth and her Carrier Strike Group to the region on its maiden operational mission later this year and a visit by Prime Minister Boris Johnson to India in April.
The UK will remain committed to NATO and the so-called Five Eyes security alliance, made up of the US, Britain, Australia, Canada and New Zealand.
It also confirmed there will be a £9m "situation centre" installed in the Cabinet Office, similar to the White House situation room where former president Barack Obama was able to watch the US special forces operation to kill Osama bin Laden in real-time.
The review, detailed over 114 pages, confirms it will hold to the NATO pledge to spend 2% of gross domestic product (GDP), and the relationship with Washington will remain close as the US is "our most important bilateral relationship".
The strategy acknowledges the risks posed by increased competition between states, including a more assertive China.
The year-long study recognises China as a "systemic challenge" but says trade relations and environmental co-operation will still be pursued.
"China's increasing power and international assertiveness is likely to be the most significant geopolitical factor of the 2020s," the review said.
"Open, trading economies like the UK will need to engage with China and remain open to Chinese trade and investment, but they must also protect themselves against practices that have an adverse effect on prosperity and security.
"Co-operation with China will also be vital in tackling transnational challenges, particularly climate change and biodiversity loss."
Russia will, according to the foreign policy brief, "remain the most acute direct threat to the UK".
Ministers judged that European and Atlantic partnerships will remain key to dealing with the threat from Moscow, along with growing threats in Asia.
Efforts will be made through legislation and by beefing up surveillance to tackle Russian disinformation, the report said.
The review also predicted that Russia would be just one of the players looking to "destabilise" the globe, with Iran and North Korea also mentioned.
For more discussion on the Integrated Review, click through to this week’s episode of the Sitrep Podcast.