Lessons for the UK Strategic Defence Review 'Home Guard'

The 2025 Strategic Defence Review has recommended additional capabilities for the protection of bases and Critical National Infrastructure and the MOD has been directed to explore the development of a new Home Defence force. The proposed force, led by the Army, could be organised under the Reserve Forces structure, have basic arms and equipment, including drones, be locally recruited and employed and have a narrowly defined remit and training commitment. The media have characterised this as a new ‘Home Guard.’ The need to protect critical national infrastructure is clear, and this would not be the first time such a force has been raised in the UK. However, the track record of such organisations raised in peacetime has historically been poor. Some basic lessons, however, could maximise the chances of success this time, and could inform the response to the Public Accounts Committee’s recommendation that by 31 March 2026, MOD sets out its plan to “significantly enhance the skills, scale and agility” of the Reserves.

The Need for Home Defence Forces?

Article 3 of the NATO Treaty, requires that countries ensure their resilience to attack, a clause that comes before the article on collective defence – Article 5. With a deteriorating security situation, as well as the disinformation and cyber attacks (already routinely underway), a path to conflict might see adversaries launching conventional pinpoint attacks to highlight vulnerabilities and sway public and political opinion. This could include drone or sabotage attacks against CNI and various choke points critical to deploying British forces overseas, while the mere threat of this would require the UK’s already too small armed forces to spread themselves even more thinly. Politicians have a track record of holding back substantial trained military resources to defend the UK even when there was no actual threat (1914-1915 & 1941-1943), so a specific Home Defence force could alleviate these pressures.

A Brand New ‘Home Guard’?

The SDR proposal for the force to be led by the Army and armed and equipped would imply a military status. As well as affording legal authority for use of violence against an aggressor, it would include enabling recompense should members come to harm, and deliver a legal right to compel members for duty. The last UK Home Guard Act (1951) gave members armed forces status, as did their predecessor organisations the National Defence Companies and Royal Defence Corps. Military status is likely as the UK does not have a history of raising civilian armed militia or paramilitaries, and any such militia proposal would have many legal and other hurdles to overcome.

Setting up a new organisation, however, costs money, often more than the original estimates, and it is already questionable that the spending review can cover the SDR’s ambitions. Costs of staff, training, accommodation, equipment, storage for weapons and ammunition would be considerable. Unless new money is made available, the new force will squeeze existing budgets, presumably MOD or Home Office, that are already under pressure. And the UK track record of funding new state organisations is poor - Home Defence always risks becoming the Cinderella of UK Defence spending.

While new organisations can initially boost marketing and recruitment, without a popular perception of a direct threat of war hanging over the country, Home Defence forces have struggled to attract civilian volunteers. The 1951 Home Guard struggled to reach 15% of its establishment and was quietly disbanded in 1957. The Civil Defence Corps of the 1950’s and 60’s also struggled to recruit. Separate Home Defence organisations can also denude the Armed Forces of volunteers in peacetime and tie down valuable individuals during a war. The 1940’s Home Guard was swiftly brought under Army control for this reason.

One of the last seriously examined proposals for a Home Guard force was in the latter stages of the Cold War. In 1982, Sir David Wills and Admiral of the Fleet Lord Peter Hill-Norton approached Margaret Thatcher with a proposal for an unpaid volunteer Home Defence force as a new branch of the Armed Forces. The Wills/Norton proposal was rejected as unrealistic. There were concerns over recruitment and training, the administrative costs, and doubts about the practical, legal and political difficulties of setting up such a large, armed, paramilitary force in peace, and the military problems of commanding and controlling it effectively in war.

The Home Service Force of the 1980’s

The Wills/Norton proposal, however, did prompt investment in the UK’s Reserve Forces of the time as a cost, and operationally effective alternative. Between 1979 and 1983 the British Army developed plans for Home Defence. The Regular Army allocated about 20,000 personnel with the Territorial Army (TA) providing another 30,000 personnel in formed units. The 1980’s Individual Reinforcement Plan involved 40,000 ex-Regular Reservists forming 170 Home Defence infantry companies, and as backfill for understrength regular and reserve Home Defence units. However, the Army wanted to free up more Regulars from Home Defence to reinforce the deployed Corps in Germany leaving the Plan more dependent on Reserves.

The Wills/Norton proposal drew attention to the high outflow both from the Regular Forces and the TA of the time. It was suggested that these trained Regular and TA leavers, could be persuaded to join a new “Home Service Force” (HSF) to guard key points. The time demands (6-10 days a year) would be much reduced from that of typical TA service (27-38+ days a year). The HSF started as a pilot scheme, recruited well and subsequently expanded nationwide.

The HSF legal and political frameworks were well established and it was defined as a ‘special force’ under the Reserve Forces Act 1980, for UK deployment only. Restricting recruitment to trained personnel enabled units to reach operational readiness quickly as there was no training burden. In total there were about 4,700 HSF across 47 sub-units, each with specific war roles to guard Key Point locations. They were administered, paid, equipped and based from local TA units in peacetime to keep costs low. In crisis they were compulsory called out like any other reservist. This allowed regular units to be released from Home Defence duties.

In addition, a plan was put in place for regionally based training organisations to churn out “Home Defence” infantry from a two-week course. The trainers would complete the training of any untrained regular and reserve recruits before moving on to training new volunteers from the public. This ‘war only’ Home Defence infantry would be formed into units and replace the Home Defence allocated regular and volunteer reserve units who moved overseas to reinforce NATO deployed forces.

The HSF Model for Today?

The HSF could provide a model for the SDR ‘Home Guard’ today. Volunteer Reserves across the RN, Army and RAF presently leave service with no recall liability. Many of these trained reservists leave due to the pressures of balancing reserve service with civilian work and family. An HSF’s lower training commitment and a UK-only mobilisation commitment could be attractive to many of these leavers. Those leaving the regular forces could also be encouraged to join. This would reduce numbers in the regular reserve, but they would be more assured than the Regular Reserve today. Legally the SDR ‘Home Guard’ could be set up as a separate special force under the Reserve Forces Act 1996 (RFA96). This would take RFA96 legislative change to enact. As with the original HSF, they could be administered, paid, equipped and based from local Army Reserve units in peacetime.

Another simpler model might be to task organise (voluntarily for training or through compulsion in war) some of the 22,000 in the Regular Reserve into Home Defence sub-units in peacetime to be ready for war. RFA96 already allows for the Regular Reserves to undertake mandatory paid training for up to 16 days a year. This would not need legislative change and so could be enacted rapidly. It might be wiser to ask for volunteers rather than use compulsion and those ex-regulars not in the Regular Reserve, but liable for recall under RFA96 (55,000 of them), could be offered an option of a transfer into the voluntary sections of the Regular Reserve (as could Army Reserve leavers). They could also be administered, paid, equipped and based from local Army Reserve units in peacetime.

An alternative could be to form a reserve force adjunct to today’s Military Provost Guard Service (MPGS). This MPGS Reserve could be similar in structure to either option above, using ex-regulars or ex-Army Reservists but would likely require some legislative backing under RFA96 or other Armed Forces legislation. This option could increase costs for the MPGS to run a Reserve Force where there is currently no tradition of doing so.

Recruiting and Funding Home Defence

All the options above use previously trained personnel. They could also take in untrained volunteers (like the current Army Reserve), but this would incur training costs and compete with the current Army Reserve numbers. The costs might be reduced by taking those from employment areas with some similar skills – ex-police for example, or even adult leavers from the cadets. Perhaps a greater risk to the force would be from any ‘Home Guard’ reserve force being allied to the current slow recruitment and training pipeline that is stifling the Army Reserve.

Army Reserve applications in the 12 months to September 2024 were at 29,800, up 45%. Yet, joiner numbers were static at about 3,000 from all sources. The current slow recruitment process loses huge numbers of applicants and the Armed Forces pre-service medical assessment is overly exacting because it is intended “to determine fitness for employment for the terms of initial engagement and (implicitly) fitness to join the Armed Forces Pension Scheme”. In taking an actuarial approach to entry, the medical bars many from service. A 90% applicant loss rate is not healthy for any organisation, has been known about for a decade, and only political leadership will now change it as the Armed Forces cannot resolve this issue themselves. A new ‘Home Guard’ would be wise to steer clear of this.

There will inevitably be demands to fund the SDR ‘Home Guard’ by removing units, or reducing paid activity, of the Volunteer Reserves, such as the Army Reserve. However. It is likely the Regular Army cannot provide sufficient numbers to NATO for deployment of the Strategic Response Corps, and the Army would need all of the current Reserve units and many Regular Reservists to supplement its regular numbers. Most other NATO nations in northern Europe are expanding their Volunteer Reserve Forces, and the SDR identifies a need for this, but gives no timeframe. Moreover, there is often a tendency to judge Reservists negatively, marginalise them and see them as a threat to the funding of Regular Forces. Extra funding for a Reserve Forces based force could be seen as a threat to the Regular force funding. Funding for the ‘Home Guard’, even if formed within the MOD, should not come from the existing Armed Forces budget but as uplift.

Other Sources of Home Defence Personnel

How much funding would be needed is unclear because the size of Home Defence demand is likely difficult to define. And depending on the scale of the demand, that would dictate whether it could be staffed by only recruiting a new HSF. Other personnel could supplement the new HSF, for example, the 3,000 MPGS. There are serving regular and reserve personnel that could also contribute to Home Defence duties. Many thousands of regular and volunteer reserve personnel are medically of limited deployability but who could be employable in guarding or Home Defence administrative roles in war. Other sources include the many regular officers and soldiers in non-deployable units/posts, the 500 Army Reservists in bands and parts of defence, such as the University Officer Training Corps, Cadet Adult Instructors and Crown Servants working for the RFCA’s, who could also be “scoured” to support Home Defence. Defence should look to maximise their own Home Defence resources, as they did in the Cold War, before looking outside for more personnel.

While trained or previously trained personnel seem the natural choice for a military HSF, this does not necessarily mean there would not be a role for civilian volunteers, or even civilian contractors. Today’s suite of surveillance assets, sensors and drones provide the intelligence to monitor threats to the UK. An expansion of this capability, in addition to the military Reserve Forces expansion, could well be provided by civilian volunteers, retired police officers or contractors and hugely boost Home Defence. This is a role that could be done without needing to enlist in the Armed Forces, and much of it could be done remotely, including from home. A modern day ‘Royal Observer Corps’ could take on the mantle of watching for threats and providing intelligence for the Armed Forces allocated to Home Defence to handle.

Summary

The SDR proposal for a new armed ‘Home Guard’ to defend CNI in wartime is sensible. Forming a modern HSF, using trained ex-regulars or volunteer reserves or building on the existing volunteer reserve structures offers a cost- and operationally-effective solution avoiding the need to create a new organisation from scratch with civilian volunteers. Expanding the UK Reserve Forces for Home Defence in this way has historically proven to be flexible, credible, more likely to recruit and most cost effective. This needs to be seen as an expansion of the UK Reserve Forces, and come with additional funding, not something to be shoehorned into existing reserve budgets. The MOD response to the September 2025 Public Accounts Committee Report calling for a clear plan for the Reserves should reflect this if this part of the SDR ambition is to be achieved.

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