Rebuilding the British Armed Forces: the Expenditure and Transformation required for the twenty-first century

The British Armed Forces have undergone profound transformations over the past two centuries. During the colonial period, Britain maintained one of the largest and most formidable military forces in the world, with the Royal Navy acting as the backbone of her global empire. The World Wars of the twentieth century saw a massive expansion of British military power, particularly in response to the existential threats posed by Germany.

At the outbreak of World War II in 1939, Britain found herself underprepared for large-scale conflict, requiring a sudden and dramatic increase in military expenditure and manpower. By 1945, the British Armed Forces numbered over five million personnel, with a formidable naval and aerial presence. During the Cold War, Britain maintained a significant standing force to counter Soviet expansion, leading to the development of nuclear weapons and the creation of the British Army of the Rhine (BAOR) to defend Western Europe.

Following the end of the Cold War, military spending was drastically reduced, driven by the belief that large-scale conventional war was unlikely again. This shift saw a transition from massed forces to smaller, technologically advanced counter-insurgency (COIN) forces, tailored for conflicts in Iraq and Afghanistan. This period also marked an increasing reliance on US military equipment and strategic partnerships, which came at the cost of independent British military capabilities.

Assessing Britain's Current Military Capability

In 2025, the British Armed Forces are considerably smaller than during their Cold War numbers in 1990 of over 310,000 personnel, 138 ships including seven aircraft carriers, 66 submarines and over 800 aircraft (not including Royal Navy aircraft, which were deployed on the fleet's aircraft carriers). This represented annual expenditure of over some 4.1% of GDP. Since then we have seen a dramatic estimated 60% reduction in the capacity of the British Armed Forces as a whole. The Army (not including the Royal Navy and the Royal Air Force) currently stands at approximately 72,000 personnel, a historic low. Contrast this with the size of the Russian Armed Forces, at approximately 1.5 million personnel, despite the Russian Federation have a population of barely twice that of the United Kingdom and a GDP of only some 6 per cent of that of Britain.

The Royal Navy now operates only a limited number of warships, with two aircraft carriers but a critical shortage of support vessels so that Britain cannot assemble an aircraft carrier strike fleet of the kind that the United States uses to project force around the world. By contrast, the United States has 11 aircraft carriers, each with a full complement of vessels to deploy a strike fleet. The Royal Air Force (RAF) has seen reduced numbers of combat-ready aircraft, and the nuclear deterrent, centred around the Trident submarine-based system, remains heavily reliant on US technology. Concerns have been raised about the adequacy of the Vanguard fleet of submarines capable of launching submarine launched ballistic missiles. Britain has only four, the same number as France; but France also has an air-launched nuclear warhead delivery capability, which Britain does not have. It is not clear that all four Vanguard class vessels may be operational at any one time; only two or three may be operational contemporaneously.

The adequacy of Britain's current military is questionable in the face of growing threats, particularly from an increasingly aggressive Russia. Britain lacks the massed forces required to deter large-scale European conflict, particularly in the event of an expansion of the Ukraine conflict. Additionally, procurement inefficiencies and reliance on foreign technology have weakened Britain's ability to operate independently in a crisis.

Required Expenditure and Transformation to a 21st-Century Military

To transform the British Armed Forces into a power capable of deterring Russian aggression and maintaining European security, significant investment is required. This includes:

1. Increasing Manpower and Readiness:

   
   

   • The British Army must expand to at least 120,000 active personnel to meet European security challenges - quite possibly substantially more. Ukraine, with a population barely more than half that of the United Kingdom, has 2.2 million members of her armed forces. Given that any future conflicts with Russia are likely to be ground conflicts, a dramatic increase in the number of British Army personnel with ground attack capacity, together with an increased number of tanks (currently about 600; Russia has an estimated 2,000 tanks in service, with another 5,000 in storage - albeit of a significantly lower quality.

     
     

   • The Royal Navy requires additional warships, including destroyers, frigates, aircraft carriers and submarines to maintain sea control in European waters and to deploy aircraft carrier strike fleets effectively.

     
     

   • The Royal Air Force must expand its fleet of fighter aircraft and drones to counter advanced Russian air capabilities, and needs to develop a strategic bomber fleet, of the kind Russia and France have, capable of delivering conventional and nuclear warheads at short and long ranges.

     
     

2. Naval Expansion:

   
   

   • The Royal Navy needs a more robust fleet, increasing from its current 19 escort ships to at least 30, including additional Type 26 and Type 31 frigates.

     
     

   • A stronger nuclear submarine force, including a fully operational fleet of ballistic missile submarines (SSBNs), is required.

     
     

   • More naval bases and logistics infrastructure to support operations in the North Atlantic and European waters.

     
     

3. Air Force Modernisation:

   
   

   • The RAF must expand its fighter jet fleet beyond the current F-35 and Typhoon numbers, potentially acquiring next-generation fighter aircraft.

     
     

   • Development and procurement of long-range strike capabilities, including hypersonic missiles and drone swarms, must be prioritised.

     
     

4. Nuclear Deterrence Investment:

   
   

   • The renewal of the UK’s nuclear deterrent must continue, with an emphasis on domestic production of key components to reduce reliance on the US.

     
     

   • Further investment in missile defense systems, including space-based early warning capabilities, is necessary.

     
     

5. Integration with European Defence Structures:

   
   

   • Given the uncertain commitment of the United States to NATO under President Trump, Britain must seek a strategic defence agreement with the European Union.

     
     

   • British forces should be better integrated into European military structures, potentially forming joint command frameworks with key EU partners like France and Germany.

     
     

Financial Commitment and GDP Allocation

A transformation of this scale will require a significant increase in defense expenditure. Current UK defense spending is approximately 2.3% of GDP, and British Prime Minister Sir Keir Starmer has undertaken to increase this to 2.5%; but to achieve a credible European defence force, this figure may need to rise to at least 4-5% of GDP—comparable to Cold War levels.

Estimated additional costs include:

• £30-40 billion for immediate manpower increases.

  
  

• £50 billion for naval expansion.

  
  

• £20 billion for expanded air force capabilities.

  
  

• £50 billion for nuclear deterrence renewal and missile defence.

  
  

• £20 billion for cyber and space warfare capabilities.

  
  

The Economic Challenge of Military Expansion

Transforming Britain into Europe's premier military power will require significant economic adjustments:

• Increased defence manufacturing in the UK, reducing reliance on foreign suppliers.

  
  

• A shift in economic priorities, potentially requiring higher taxation or reallocation of government spending.

  
  

• Recruitment drives to increase manpower, requiring incentives to attract talent to the armed forces.

  
  

Conclusion: The Strategic Necessity of Military Reinvestment

With European security under growing threat from Russian aggression, the UK must reassess its military capabilities. The assumption that the United States will always provide European security guarantees is increasingly uncertain. As NATO faces potential fractures, Britain must be prepared to assume a greater role in maintaining the balance of power in Europe.

A substantial increase in defence spending is required—not only to modernise equipment but to rebuild a force capable of deterring Russian aggression independently if necessary. This will demand strategic decisions regarding military-industrial investment, force expansion, and European cooperation.

Failure to act could leave Britain—and Europe—exposed in the face of an emboldened Russia. The costs are high, but the price of inaction may be far greater.

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[Of the nuclear bomb] "We've got to have this thing over here,

whatever it costs. We've got to have the bloody Union Jack on top of it.

Ernest Bevin, British Foreign Secretary (Labour), 1947