Britain’s military is to get an £80 billion upgrade as the Government announces a modernisation drive this month to get the Armed Forces ready for the wars of the future.

The Telegraph understands that is roughly what will be invested in improving military equipment over the next four years. The total over the next decade could amount to close to £200 billion.

More than a hundred ageing Challenger 2 tanks will get new turrets, guns, sensors and engines, becoming more deadly in the battlefield, while new frigates are being acquired.

The cap on the number of nuclear warheads Britain can stockpile will increase from around 180, The Telegraph has learned, ending a decades-long drive to cut stocks.

There is also a new push underway to acquire what are called loitering munitions, sometimes dubbed “kamikaze drones”, which can hover around a target before donating.

There has been alarm that hostile nations such as Russia and Iran have been using such munitions, which are a cross between cruise missiles and armed drones.

One senior government source said: “Technology has proliferated, that’s what we should worry about. Everyone from terrorists to other nations have modern equipment and killer drones.”

The moves form part of a major rethink of Britain’s defence, foreign policy and security outlook, with results to be revealed in two government documents over the coming fortnight.

The first, the UK Integrated Review, will be published on Tuesday. It will map out what the Prime Minister’s ‘Global Britain’ vision means in practice, including a tilt to the Indo-Pacific.

The second, the Defence Command Paper, will come out March 22. It will reveal a major modernisation plan for the Armed Forces, seen as long overdue by defence chiefs.

The proposals will include cuts to troop numbers and the scaling back of so-called “legacy platforms”, which are parts of the military that have been prominent since the 20th century.

Government figures have stressed that such changes should be seen as “retirements” rather than “cuts”, given the overall Ministry of Defence budget is increasing.

“To modernise, some things have to be retired. Otherwise the musket would still be on the field,” a senior government source said.

The changes will affect all branches of the Armed Forces, the Army, Royal Navy, RAF, and Strategic Command, which oversees cyber attacks.

The focus on so-called kamikaze drones reflects how rapidly combat is changing in the battlefield, with nations (including adversaries) increasingly investing in them.

A senior defence source said: “We’re seeing them used all over the place. How to counter the capability and how to use it are two things there is a lot of interest in.”

How Government is preparing for wars of the future

Boris Johnson has billed the integrated review into Britain’s foreign, defence and security policy as the most radical overhaul of the nation's posture since the end of the Cold War.

The review will be published on Tuesday, while on March 22 a Defence Command Paper will set out the Government’s plan for a generational modernisation of the Armed Forces.

The Prime Minister unveiled a £16.5 billion funding uplift for the Ministry of Defence (MoD) over the next four years at the spending review last November to fund the strategy.

The challenge for Ben Wallace, the Defence Secretary, and the service chiefs, has been to balance pouring cash into upgrading legacy platforms with investment in cutting-edge military technologies.

© Provided by The Telegraph Prime Minister Boris Johnson greets troops alongside Northern Ireland Secretary Brandon Lewis (right) and Brigadier Chris Davies, Commander 38 (Irish) Brigade (left), during a visit to Joint Helicopter Command Flying Station Aldergrove in Northern Ireland - Peter Morrison/PA

Nuclear Deterrent

Britain is set to publicly declare on Tuesday that it is increasing the number of nuclear warheads it can stockpile, The Telegraph understands. At present the UK has around 180 nuclear warheads.

The Government has already confirmed it is replacing the existing warheads that are used in the Trident nuclear deterrent. Ministers have also committed to building four new Dreadnought Class nuclear attack submarines to replace the current Vanguard boats by the middle of the next decade.

© Provided by The Telegraph Royal Navy Vanguard Class submarine HMS Vigilant returning to HMNB Clyde after her extended deployment - CPOA(Phot) Thomas McDonald/Royal Navy

Defence sources said research collaboration between the UK and US was expected, but the MoD confirmed on Thursday night that both the warheads and submarines would remain independent, sovereign programmes.

The heightened cap is due to be unveiled amid fears about China’s swelling nuclear stockpile.

Sam Armstrong, of the Henry Jackson Society foreign policy think tank, said: “The world is an increasingly dangerous place and this increased nuclear deterrent tells us all we need to know about where the long term threat from China is heading.”

Experts on nuclear non-proliferation stressed how striking a move the policy would be.

Matthew Harries, a senior research fellow in nuclear policy at the Royal United Service Institute, said: “An increase in the UK’s declared nuclear stockpile cap, if confirmed, would be a significant reverse of steady disarmament progress since the end of the Cold War."

Tanks and armoured vehicles

The Army’s ageing Challenger 2 tanks require an urgent upgrade to their turrets, guns, sensors and engines. Around 150 to 170 of the UK’s 227 tanks will be upgraded, according to defence sources. The remainder will be mothballed for spares, it is understood.

All 758 Warrior infantry fighting vehicles are meanwhile expected to be “abandoned” from next year. They are set to be sold off to save money, insiders have said.

This decision will be balanced by a move to accelerate the introduction of more than 500 Boxer mechanised infantry vehicles.

These vehicles are set to arrive next year to avoid a gap between the two programmes. A Whitehall source signalled the programme would also be expanded, saying: “We are increasing the order of Boxer and that’s the right thing to do.”

Question marks hover over the future of the Army’s high-intensity armoured warfighting capability, if the modernisation does not also boost field artillery and air defence systems.

Troop numbers cut

The Army is set to fall to around 73,000 soldiers, finally abandoning its minimum threshold of 82,000 personnel – a target it has not met for years.

A formal reduction to the service has been on the cards since December 2019, when Boris Johnson dropped the pledge from the Tory election manifesto.

Its current full-time trained strength is 76,348. Service chiefs are set to rely on the organic departure of troops, due to resignation or retirement, to reduce the headcount rather than make personnel redundant, it is understood.

Fighter jets

Britain is expected to pull back from its previously stated ambition to buy 138 F-35 Lightning II fighter jets, which are the most expensive weapons system in military history.  The UK is so far only contractually obliged to buy 48 of the stealth multi-role fighter jets by the end of 2025, at a cost of £9.1 billion.

The US-designed fifth-generation jets will be bought in tranches over many years, however, meaning decisions about future orders can be thrown into the long grass, avoiding confrontation with Washington now about the final order numbers.

The higher cap will signal a new direction from Britain on nuclear non-proliferation, making a firm statement on the nation's position as a nuclear power.

Investment is also being poured into Tempest, a UK-led programme to develop a sixth-generation fighter jet. One design option is for this to be an unmanned aircraft.

© Provided by The Telegraph Engineers at BAE Systems are exploiting the digital environment to design, test and fly conceptual models for Tempest, a next-generation combat air system for the UK

It is also set to be accompanied in flight by a swarm of unmanned combat drones known as “loyal wingmen”.

Innovative weapons

The use of loitering munitions, which are a cross between cruise missiles and armed drones, by Russia, Iran, Azerbaijan and other nations has been watched closely by the MoD.

Defence chiefs have pushed for the UK to invest in developing a domestic capability. “We need to develop these capabilities, test them, experiment with them and work out how best to employ them. That might require some changes to how we organise the way we fight,” said a defence source.

© Provided by The Telegraph A Harop loitering munition (LM) system. The unmanned combat aerial vehicle loiters over the battlefield and attacks the targets by self-destructing into them

More investment is planned for autonomous, AI-enabled systems, including both aerial and underwater drones, as well as land-based robots.

Unmanned capabilities are particularly attractive because they avoid the need to put personnel at risk of harm.

Fresh focus on the Indo-Pacific

© Provided by The Telegraph 252239458 / c69af9a5-436b-3491-9f76-c58a8f41025a Image headline: HMS Queen Elizabeth Departs From Portsmouth Navy Base Original description: PORTSMOUTH, ENGLAND - MARCH 01: HMS Queen Elizabeth departs from the Naval base on March 01, 2021 in Portsmouth, England. The £3 billion aircraft carrier is expected to undertake an additional series of sea trials in preparation for her first active deployment planned to begin in May. - Finnbarr Webster/Getty Images

The review is expected to set out the Government's post-Brexit “Global Britain” vision, which includes a new emphasis on the Indo-Pacific.

HMS Queen Elizabeth, the first of Britain’s two new aircraft carriers which have collectively cost more than £6.2 billion, is due to set sail on its first operational deployment around late April.

It will sail to the Mediterranean, the Indian Ocean and east Asia, into China’s backyard, testing freedom of navigation rights.

Defence chiefs are also examining plans to “forward base” more personnel and assets (including warships) overseas in the Middle East and Pacific regions. Bases and ports in Japan, Australia and Singapore have been scoped out as potential options by officials.

Britain has already confirmed plans to triple the size of its military base on the coast of Oman to enhance the Royal Navy's presence "east of Suez" after Brexit.

Boost to fleet and shipyards

The Prime Minister has announced that the UK will acquire eight Type-26 frigates, which are sophisticated anti-submarine warships, as well as five Type-31 frigates, cheaper general purpose warships.

His plan is to restore Britain’s position as “the foremost naval power in Europe”, he said last autumn, as he also confirmed plans for new support ships to supply food and ammunition to the aircraft carriers, and new multi-role research vessels.

Combined, the programmes are set to support up to 10,000 jobs and are seen in Whitehall as a boost to the Union as shipyards in Scotland and Northern Ireland are set to benefit.

New organisations

A long-delayed National Cyber Force, a joint unit between the MoD and GCHQ, is being created to boost protection to Britons at home as well as to develop new offensive cyber weapons to deploy against adversaries overseas.

RAF Space Command is expected to be capable of launching its first rocket by 2022 and will aim to better shield the UK’s satellites. A new Artificial Intelligence agency is meanwhile set to develop autonomous weapons systems.

Stressing the importance of data in future conflicts, a senior Whitehall source said: “What’s certain is that the future will be about cyber, space, AI.”

An MoD spokesman said: “As threats change our Armed Forces must change and they are being redesigned to confront future threats, not re-fight old wars. The Armed Forces will be fully staffed and equipped to confront those threats.

“We will not comment on speculation about the Integrated Review, which will be published on Tuesday.”

The UK Integrated Review is understood to be around 100 pages long and entitled "Global Britain in a Competitive Age".