The UK government on Monday unveiled its much-anticipated military modernisation plans, bolstering the country's navy, special forces and global focus while cutting the size of the army.

The long-awaited proposals promise new investment in ships, submarines and sailors, as well as robots, drones and cyber warfare, alongside an overhaul of the land-based armed forces structure and numbers.

Publishing the 70-page report, titled "Defence in a Competitive Age", Defence Secretary Ben Wallace told lawmakers the government's strategy marked a shift "from mass mobilisation to information age speed, readiness and relevance".

"We will ensure defence is threat-focused, modernised and financially sustainable, ready to confront future challenges, seize new opportunities for global Britain," he said, calling it "an honest assessment of what we can do and what we will do".

"We will for the first time in decades match genuine money to credible ambitions," Wallace added, noting that would mean retiring some platforms "to make way for new systems and approaches".

However, the decision to reduce the army's size to 72,500 by the middle of the decade, from an established strength of 82,000, could prove contentious domestically and among allies.

Military experts in the United States have already expressed alarm at the move, while opposition parties in Britain also voiced concern.

"Useful"

The reforms follow a commitment by Prime Minister Boris Johnson last November to increase defence spending over the next four years by 16 billion pound ($22 billion, 19 billion euros).

They also come hot on the heels of last week's broader overhaul of Britain's security, defence and foreign policy, billed as the biggest since the Cold War.

Crafted over the past year as London recalibrates its post-Brexit foreign policy, that review outlined a pivot in strategic focus towards Asia, labelling China a "systemic competitor".

It also prioritised ongoing efforts to counter Russian threats and, in a surprise move to many, set out plans to increase Britain's nuclear stockpile.

Johnson said ahead of Monday's plans being released that Britain wanted "to be useful around the world in partnership with our friends to keep the peace".

"To do that, you need strong, robust armed services of the kind that we are investing in," he added, during a visit to BAE Systems in northern England.

"Collective deterrence"

The defence review set out key spending priorities, including funding to take the number of navy frigates and destroyers to 20 by the start of the next decade.

It also detailed that Britain will expand its fleet of US-made F35 fighter jets only to 48, the minimum number it had committed to buy.

The document earmarks 200 million pound of investment over the next decade to transform the Royal Marines into a new unit called the Future Commando Force.

It will conduct roles traditionally carried out by UK special forces and be deployed on "an enduring basis" to help secure shipping lanes and uphold freedom of navigation.

The review also pledges 120 million pound to establish an army special operations brigade and a new Ranger Regiment.

It will "be able to operate discreetly in high-risk environments and be rapidly deployable across the world" and involved in "collective deterrence" with partner forces.

A new Security Force Assistance Brigade will provide guidance and training to allied partner nations and draw expertise from across the army.

Meanwhile the Royal Navy will develop a new surveillance ship, to come into service by 2024 with a crew of around 15 people, aimed at protecting Britain's undersea cables and other critical national infrastructure.