Britain’s armed forces will undergo the most comprehensive modernisation in two decades, as the UK takes a “more robust” stance over the “deteriorating” global security environment.

The Integrated Review (IR) sets out plans to update the country’s “deterrence posture” in the face of growing threats from hostile states and non-state actors.

It says the UK must improve its ability to “disrupt, defend against and deter” the threats it faces in both the physical world and in cyberspace.

It will mean deploying more of the armed forces overseas more often and for longer periods, in an effort to deter state threats “below the threshold of war” through a strategy of “persistent engagement”.

“We will demonstrate that we are able and willing to respond when our citizens and interests are targeted, including with force if necessary,” the IR says.

At the same time, the Government is lifting its self-imposed cap on its stockpile of Trident nuclear warheads from 180 to 260.

The move is said to be in recognition of the “evolving security environment”, including the developing range of “technological and doctrinal threats”.

A defence command paper to be published next week will set out the detailed plans to modernise the armed forces, with a new generation of warships and fighter jets.

It will also include a major overhaul of the Army, which is expected to be cut by around 10,000 troops, with the force Challenger 2 main battle tanks reduced by a third and the Warrior infantry fighting vehicle axed altogether.

The IR says it will prioritise the development of new technologies, with a “digital backbone” to enable UK forces to operate alongside allies across a range of battlespaces.

As well as maintaining an offensive cyber capability, there will be a new “space command” and measures to improve CBRN (chemical, biological, radiological, nuclear) resilience.

Overall, the review says the primary focus of Britain’s security effort will remain the Euro-Atlantic region, where Russia poses the “most acute threat”.

However, in the face of China’s growing power and assertiveness – described as “the most significant geopolitical factor of the 2020s” –  there will be a new  “tilt” towards the Indo-Pacific.

It will be marked by the deployment to the region later this year of the HMS Queen Elizabeth carrier strike group on its maiden operational deployment.

“The significant impact of China’s military modernisation and growing international assertiveness within the Indo-Pacific region and beyond will pose an increasing risk to UK interests,” the IR says.

“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.”

The review highlights the security threat from the “opportunism” of countries like Iran and North Korea as well as from Russia.

It says such state threats include espionage, political interference, sabotage, assassination and poisonings, electoral interference, disinformation, propaganda, cyber operations and intellectual property theft.

“While their actions often fall short of open conflict, they can nevertheless threaten and interfere with our security, open economy, democracy and social cohesion – risking escalation into war,” it says.

“Non-state actors also participate in this competition. They often use the same methods, such as cyber-attacks and disinformation, to target our citizens and exploit our openness for their own gain.

“And states increasingly work with non-state actors to achieve their goals, including as proxies in conflict.

“This affords them deniability and blurs the line between state threats and other types of security threats, such as terrorism and SOC (serious organised crime).”