The Strategic Defence Review, launched in July 2024, said it would “put personnel at the heart” of the UK’s defence.
What is the Strategic Defence Review?
The Strategic Defence Review was commissioned by the government shortly after taking office in July 2024. The review was independently led by former Defence Secretary and former NATO Secretary General, Lord Robertson. The government has endorsed the review and accepted all 62 of its recommendations. The government published the Strategic Defence Review on 2 June 2025.
Responding to a question from the Liberal Democrat leader, Ed Davey, the Prime Minister, Sir Keir Starmer, said that the “low numbers of troops” will be looked at as part of the review.
What is the size of the UK’s armed forces?
On 1 April 2025, the total size of the full-time UK armed forces (trained and untrained) was around 147,300 people. This number comprises all full-time trained and untrained members of the UK Regular Forces, Gurkhas, and full-time Reserve service personnel.
Over half of personnel were within the British Army (56%), with the remainder split between the Royal Navy/Royal Marines (23%) and the Royal Air Force (RAF, 22%).
In its September 2024 report on Ukraine, the House of Lords International Relations and Defence Committee said it was concerned that the Army would not be able to meet the expected troop contribution to NATO. The committee said that it “therefore question[s] whether the British Army is prepared to meet the growing threat posed by Russia to European security.”
Is the size of the UK’s armed forces low in historical terms?
Historical figures on armed forces personnel refers to UK Regular Forces. This is the main body of permanent personnel in the UK armed forces (both trained and untrained). This measure excludes Gurkhas, reservists, and other personnel categories.
The number of full-time armed forces personnel was significantly higher during the First World War and Second World War, reaching 4.6 million in 1918 and 4.9 million (its peak) in 1945. The number of armed forces personnel declined sharply in the five years following each war:
- by 93% between 1918 and 1923 to 335,000
- by 86% between 1945 and 1950 to 696,000.
As shown in the charts below, there has been a general downward trend in the number of Regular Forces since 1952.
Between the end of mandatory National Service in 1960 and 2025, the number of UK Regular Forces personnel has fallen by 74%. During this period, the number of personnel fell by around:
- 184,000 (71%) in the Army
- 136,000 (82%) in the RAF
- 66,000 (67%) in the Royal Navy
Recruitment and retention
The total number of people both joining and leaving the UK Regular Forces has decreased between 1999/2000 and 2024/25. As shown in the chart below, between 1999/00 and 2023/24, there have only been six years when inflow was higher than outflow, meaning more people joined than left.
The number of people joining the UK Regular Forces fell from 25,550 in 1999/2000 to 13,450 in 2024/25 (a 47% reduction), while the number leaving fell from 26,620 to 14,590 (a 45% reduction). The largest net fall in armed forces personnel was over the period of the redundancy programme, which was implemented to meet the reduced personnel levels determined by the 2010 Strategic Defence and Security Review. More information on the redundancy programme can be found in section 3.1 of the Commons Library research briefing UK defence personnel statistics.
In the 12 months to 31 March 2025, there was a fall in the overall number of Regular Forces personnel, with around 1,140 more personnel leaving than joining. This was a lower net decrease than the previous year, when 4,430 more personnel left than joined, because of an increased intake between 2023/24 and 2024/25, and a slight fall in outflow.
Voluntary outflow was the most common reason for leaving for full-time-trained and trade-trained members of the Regular Forces, accounting for 62% of total outflow. In a February 2024 report on the readiness of the armed forces, the Defence Select Committee raised concerns about issues with recruitment and retention in the UK armed forces.
In oral evidence to the Public Accounts Committee in April 2025, the Chief of the Defence Staff, Admiral Sir Tony Radakin, acknowledged the problem with recruitment and retention in the armed forces but said “it is easing”. He added that “the forecast is that it will bottom out and that we will start to rise across the whole of the armed forces in the next two to three years”.
What has the review said about armed forces personnel?
The review set out that a workforce crisis had been caused by “poor recruitment and retention, shoddy accommodation, falling morale, and cultural challenges”.
The review recommended that “in the current strategic and fiscal situation” the number of Regular Forces should not be reduced. However, budgetary restraints meant increasing the number of Regular Forces cannot yet be considered:
The Army must evolve its mix of Regulars and Reserves, with a minimum of 100,000 soldiers, of which 73,000 are Regular. A small uplift in Regular personnel should be considered when funding allows (accounting for the costs of equipping and training these personnel).
When making his Statement to the House, Defence Secretary, John Healy said “reversing the decline will take time”, noting that the target to increase the British Army to 76,000 full-time soldiers will be “in the next Parliament”.
The report also highlighted that enhancing the standards of Service Family Accommodation and Single Living Accommodation is “essential to morale and retention”. To address retention issues, among other things the review recommended that “Defence should explore options to support Service personnel’s aspirations for home ownership”.
As part of the review, £1.5 billion was committed for rapid work to fix the state of forces family housing. This means over “£7 billion will be spent” on military accommodation in this Parliament.
Further information
More information can be found in the Commons Library research briefings UK defence personnel statistics and The forthcoming strategic defence review 2025: FAQ.
The Commons Library research briefing A brief guide to previous British defence reviews summarises the main recommendations that have been made in defence reviews since the end of the Second World War.
About the author: Niamh Foley is a statistics researcher at the Commons Library.
Photo by: Sergeant Peter George via Ministry of Defence
