UK Defence Spending: Is 2.5% Enough?
A brief overview of UK Defence policy
In light of Putin’s war of aggression in Ukraine, and The United States’ lurch towards authoritarian fascism and betrayal of its allies, European countries are talking about increasing their defence budgets. I fully support this. One question is whether the numbers being put forward for defence spending in the UK are high enough to meet defence capability requirements.
It is worth noting that my calculations here are incredibly rough, for example, I am not factoring in anything like growth in UK economy or inflation and am definitely missing many key variables from my assessment around costs involved in defence such as procurement, maintenance and training. It is also worth noting some data may be inaccurate, particularly for Russian forces, and whilst I am making conservative estimates about what UK forces can actually deploy of the equipment they have, I don’t have as much information what proportion of Russian assets are deployable in some cases.
I also want to clarify —
This is NOT my area of specialisation.
This post is certain to include some errors — the modelling about how defence budget is spent particularly makes a LOT of assumptions. I believe this low resolution assessment is still good enough to evaluate whether or not 2.5% is sufficient to meet UK defence requirements.
I am NOT taking myself to be an expert in defence or anything like that — I wrote this in bed on a Sunday morning to try to better understand my thinking and I hope this to be a useful clarificatory post for people to understand UK defence policy and spending if they previously had no idea about it. This is NOT an expert, detailed, opinionated analysis of the best thing the UK could do. If you want something more like that you can read experts on substack like
Preamble
Main Adversary
I am assuming that the UK should consider Russia its main defence adversary. Here are some facts about the Russian Armed Forces:
Army:
Navy:
10 Destroyers
12 Frigates
83 Corvettes
1 Air Craft Carrier
Air Force: 541 Fast Jets
Budget: 6.7% GDP ($145.9bn)3
Defence Role
In any major conflict with Russia, the UK would be working with other EU countries. I shall discuss some of the main strategic concerns of the UK alongside potential roles it would play in a European defence force whilst also noting existing responsibilities and deployments that would have to be maintained.
The main role of the UK would be associated with protecting safe global trade routes.
The UK economy is highly dependant on global trade with the total value of trade in the UK in 2024 being £1,703.4 billion4.
[Edit]:
pointed out here:the trade numbers … are for goods and services. More than half of UK exports are services, and in particular it's two thirds to the US. So most of that £180bn exports to the US isn't being transported in a container.
Although it probably is going through those undersea cables.
— the point about undersea cables shall be covered shortly…
The UK, as an island nation is also a net importer (i.e. dependent on trade) for its food security (either in terms of food imported, or goods required for UK producers)5.
One of the UK’s key strategic concerns is defending The GIUK Gap6.
This is because many of the primary Russian Naval bases are located along Russias Northern coastline.
This makes this corridor the main route of travel for Russian vessels (including nuclear armed submarines) entering the Atlantic,, for Russian vessels aiming to reach The Mediterranean or Africa, for an invasion force aimed at the UK, or Greenland and for maritime espionage missions targeting critical infrastructure like pipelines or undersea cables critical for business and financial institutions.
Since the cold war, and continuing under Putin, the Russians have tested UK air defences by regularly flying Bombers over Scotland.
The Russian military has many bombers capable of carrying conventional and nuclear payloads. In the event of a war, it is clear that there would be Russian bombing missions into UK airspace. This may also include the use of targeted cruise missiles which would probably come from the same attack vector. As a result, it is crucial for the UK to develop and maintain a comprehensive defence strategy for its airspace including an enhancement of existing radar facilities, such as RAF Flyingdales (responsible for detecting ICBM launches), surface to air missile capabilities (particularly for the threat of cruise missiles and potentially ICBM’s) and an enhancement of our current QRF fighters for protecting UK air space.
In 2022, Nordstream gas pipelines between Europe and Russia were attacked in an act of maritime espionage7. Since then, the Russian “shadow fleet” has engaged in a series of increasingly confrontational and combative actions threatening the UK and Europes underwater infrastructure.
Around 600 undersea cables carry electricity and information across vast oceans and seas. Coming ashore often at discreet, secret locations, all 870,000 miles (1.4m km) of them connect us. The majority are data cables, responsible for almost all of our internet traffic.8
There have been a number of subsequent attacks to European undersea infrastructure documented in that article.
Russia have been signalling their intent to damage UK undersea infrastructure for a while, for example planning Naval exercises off the coast of Ireland directly over critical underwater infrastructure for the UK in 20229, through various incursions leading to a recent event where a Royal Navy Nuclear submarine surfaced in front of a Russian vessel in November 2024 chasing it away from vital infrastructure10
Mr Healey confirmed that Yantar entered the UK’s Exclusive Economic Zone (EEZ) on Monday, approximately 45 miles off the British coast. The vessel is believed to specialise in gathering intelligence and mapping critical underwater infrastructure.
“For the last two days, the Royal Navy has deployed HMS Somerset and HMS Tyne to monitor the vessel every minute through our waters…I authorised the Royal Navy submarine to surface close to Yantar, strictly as a deterrent measure, to make clear that we had been covertly monitoring its every move”
Defending undersea, critical infrastructure is one of the key strategic aims of UK defence forces.
The UK also has defence interests in the Mediterranean. At Gibraltar, the UK has the capability to police naval entry into the Mediterranean through its military base.
The UK also has a military base in Cyprus which has the capability to re-arm ships, launch
This base can also act as a launch pad for sending UK forces to regions like Ukraine, or for launching aerial missions in the Black Sea where a Russian fleet is stationed.
The UK has also been responsible for defence operations in Estonia as a part of NATO’s Enhanced Forward Presence deployment.
Following Russia's invasion of Crimea, NATO's member states agreed at the 2016 Warsaw summit to forward deploy four multinational battalion battle groups to areas most likely to be attacked.11
The UK is committed to some defence capability in Estonia, which includes thousands of personnel, several main battle tanks, multiple helicopters and artillery. Whilst it is not clear what NATO’s strategy will be with respect to the Enhanced Forward Presence in light of its largest contributor recently deciding to side with its enemy, it is fair to say that as long as the UK has this government in power we will also be committed to defence agreements we have made with our allies.
The UK has also committed to a 100 year security guarantee with Ukraine12. There are also talks of a potential deployment as part of a peacekeeping force13
in Ukraine. In the event of a war with Russia, it is clear that the UK would be potentially be engaged in deployments within the Ukrainian region. However, it is not easy to say exactly what that might look like, especially given how current deployments essentially exhaust the personnel and equipment capabilities of the Army.
The British Armed forces would also have to keep up defence efforts globally, where it has the following current deployments Globally14.
Most importantly and costly of these is the UK’s defence commitment to the Falklands Islands 12955km away from London. The Falkland Islands were invaded by Argentina in 1982 and successfully defended by the UK leading to an Argentine defeat and peace with ongoing hostilities. Whilst some may consider the UK’s sovereignty over an island so far from its shoreline an immoral act of colonialism, the truth is that questions of democratic self-determination have been an important part of UK politics for a while with a referendum on independence taking place in 2013.
On 10-11 March 2013 the Falkland Islands Government held a referendum on whether or not to maintain the Islands’ status as a British Overseas Territory. There were 1513 votes (99.8%) in favour and three against. The turnout was 92% of an electorate of 1653.15
Given the Falkland Islanders desires to be a part of the UK, and the threat posed by Argentina, there is a permanent garrison on the Falkland Islands including 4 Eurofighter Typhoon TR1 jets, 1 River Class OPV (HMS Forth), 40 strong Island Defence Force (locals) and ~1500 personnel which includes hundreds of infantry, logistics and maintenance personnel, air traffic controllers, engineers etc.16
Putting Some Rough Numbers on Things
Current UK Armed Forces Capabilities
Army:
Deployable Infantry: ~20,00017
Main Battle Tanks: 213
Navy:
Destroyers: 2 (a further 4 in re-fit)
Frigates: 8 Commissioned, 6 in active service, 2 in re-fit
Air Craft Carriers: 2
Air Force:
Fighters/Fighter-Bombers: 167
AWACS: 3
Transports: 32
Tankers: 14
Budget: 2.32% GDP ($68.1bn)
These numbers hide some of the complexity inherent in the fact that some equipment may be in storage but not immediately ready for deployment, or may not have the logistics required to be deployed, or the required number of maintainers to be supported. This is another assumption that makes this model very very rough around the edges.
For example, the UK has both Eurofighter Typhoons and F35 fighters. These are “available” in various states, for example:
Britain currently has 34 F-35Bs, with HMS Prince of Wales deploying on CSG25 later this year with 24 British F-35Bs embarked.
[Edit:] A note on available planes on aircraft carriers thanks to u/MGC31
So, those 24 “embarked” F35’s are procured but not in-service yet as they have not been requested for deployment on either of the UK’s two aircraft carriers.
Given the scale and range of UK defence deployments globally and the potential demands on the UK as a European leader in the event of a war with Russia, these numbers are not high enough to be very confident in the UK’s ability to successfully defend itself against Russia or to proactively engage in a conflict on the offensive.
Things are in fact even worse than a simple comparison of the numbers would indicate. Problems associated with manpower and equipment shortages are compounded by years of managed decline through austerity with the UK armed forces shrinking by 30% since 200018 , this has led to the loss of skills and capabilities from the armed forces with the loss of training programmes, attrition out of the services of personnel with combat experience, pivoting capabilities towards fighting the asymmetric “war on terror” (hence pivoting away from capabilities for conventional warfare) — these problems affect naval personnel, infantry units and pilots.
Again, in this area modelling the right thing to do is quite difficult. The UK has a relatively broad organisational structure and it could be the case that in the event of a war that’s the right sort of thing to have in place so as to “fill out” capabilities that are currently stretched thin.
“The proportion of infantry within the Army is probably about right, it's just spread too thin across too many units, presumably in order to keep up appearances and avoid cutting battalions, meaning many are terribly undermanned. The units themselves are spread across too many formations without the necessary support to actually do anything. Most obviously, the 4th Light Brigade, which has one regular cavalry regiment and six (6!) regular infantry battalions, but all the other roles - artillery, engineers, signals, and logistics - are provided by reserve units. This makes it incapable of deploying as a brigade.
By all means make an argument for increasing overall headcount, but just trying to grow the number of frontline troops/units will only compound this problem. It pains me to say it as it likely means historic regiments will be lost once again, but realistically if the Army doesn't get any bigger we'll need to reorganise the infantry we have into 20-25 battalions rather than 33.”
( thanks to u/memmett9 on reddit for this)
Again, modelling the complexities of what that would/should look like is beyond the remit of this piece and outside my area of expertise. It seems like quite a complicated area with a lot of domain expertise required to fully understand how to “flesh out” the required skills, infrastructure, command structure and “scale” it up.
Obviously any war with Russia would be part of a combined effort with other European nations. One thing to note here is that many European nations are in a worse state than the UK are and many look to the UK as a leader on defence.
The point here is that we aren’t exactly comparing the UK fighting Russia on its own with no European support. And, on that front things look somewhat optimistic, combined together as they stand (on paper at least) the European nations collectively have a lot of man power and a lot of kit — Definitely a threat to a place like Russia. The key questions from the UK perspective though are whether we have enough to “scrape by” or be confident we can win. Whether we have the ability to avoid massive damage and loss within the UK by having adequate defences. Whether we would be able to maintain our global presence. For example, a mainland war in Europe and a severance of ties with the US could incentivise Argentina to give taking the Falklands another shot whilst we’re wrapped up defending our undersea cables and Estonia!
What 2.5% Could Get Us
The idea here is to use numbers to get a very very rough intuition for the magnitude of investment a 2.5% spend would constitute. Based off of the proposed increase to 2.5% of GDP, is this enough to salvage our declining armed forces and meet our defence capability requirements?
Given the UK’s current force composition and interests, how might that be spent?
Most of the UK’s commitments and concerns are maritime. At the moment the prospects for the Royal Navy are quite dire:
“Britain can no longer deploy large numbers of Warships to sea as we simply don't have large numbers of Warships. What we do have are a small number of Warships with quite a number of them currently in refit, mothballed or lacking sufficient crew due to the dire state of Royal Navy recruitment. Of the Type 45 Destroyers [we have], six are in commissioned service, but only two of them are actually in active service today. The rest are in refit. Of the Type 23 frigates, eight are commissioned and six are in active service with two currently being refitted.”
[Edit:] It has also been pointed out to me that buying a single unit-item as if you were purchasing something off the shelf isn’t exactly how this would work. This means that my modelling here is a bit inaccurate for what would happen in reality. That being said, even spending the money over multiple years in chunks on things like ships being built, you’re only spreading a finite amount of money over a finite number of years within which you have the defence risk of not having the asset you’re acquiring… While creative accounting may lead to some benefits in the case of a real allocation of this budgeting, I think that keeping the model simple is probably best for illustrating the “reach” of the available funds.
The Royal Navy currently only has TWO of it’s modern Type 45 destroyers that are combat ready and functional if the need came for a deployment today.
The cost of a Type 45 Destroyer is £1.05bn per ship (yes, it should be spread out over years) -- £11mn / yr to run (peacetime)21. Making many many assumptions, that would put the cost for just TWO more at ~£2bn. Almost half of the proposed spending increase…
The other key capability gap is in terms of deployable front-line infantry. We have commitments in the Falklands, for home defence (i.e. the coastline, or against paratroopers were we to be at war) and in Estonia and possibly Ukraine. Yet, we can currently only field a maximum of ~20k troops.
It costs ~£47,800 to train a British infantryman22 and £47,352 a year for their upkeep (peacetime). Again, making many many assumptions, that would put the price for 20k new troops at ~£1bn. Note that in the current Ukrainian war, the Ukrainian armed forces are losing approximately 200 personnel a day23 — at that attrition rate, this number of infantry would be completely eliminated within 100 days.
In the RAF, we currently have 33 F35 Pilots (incl some Australian and US servicemen)24. We have ~20 fast jet pilots in training25. 130 Eurofigher Typhoon aircraft 130, 37 F35 stealth-figher aircraft. 3 Wedgetail AWACS aircraft, 9 air to air refuelling aircraft.
It costs approximately ~£5 million to train a fast jet pilot26. The cost per unit for an F35 or Eurofighter Typhoon is ~£95 million27. This puts the cost for +8 fighter at £0.76 billion, and for an additional 48 fast jet pilots (making up for the current shortage) to £0.24 billion.
That would exhaust the ENTIRE proposed increase in defence budget.
What would our TOTAL armed forces be after this budget increase with these very optimistic procurements?
Army: +20k deployable infantry
Navy: +4 working modern destroyers
Air Force: +8 fast jets and bunch of pilots for existing ones.
Bringing us to something like:
Army:
Deployable Infantry: ~40,000
Main Battle Tanks: 213
Navy:
Destroyers: 4 active (with 4 in re-fit)
Frigates: 8 Commissioned, 6 in active service, 2 in re-fit
Air Craft Carriers 2
Air Force: Fighters/Fighter-Bombers: 175
Budget: 2.5% GDP ($73.3bn)
So, after these changes the forces comparison to Russian might look something like (again a great many assumptions).
So, is 2.5% enough?
On the optimistic side, I do think there are some good things here. The UK is probably able to defend its waters and skies from Russian aggression — given the distance of travel from Russia to the UK, and the involvement of other European allies, it’s unlikely that Russia would be able to more effectively fight the RAF and Royal Navy in the waters and skies around the UK. If you combine that with capabilities from the other European nations, there is clearly a force that can seriously challenge Russia. The downside of all this is that it isn’t as clear (as is the case with US+European combined forces) what the risks are, it isn’t overwhelmingly one sided. And IF the US were to abandon European nations, and (say) China, or India or North Korea were to become more involved in a Russian war against European nations, it becomes less clear how good the picture is with the current European defence capabilities
The other considerations are maintaining existing roles across the world. The UK armed forces have been in a state of managed decline for a while and are in a stretched position as things stand. Taking on additional responsibilities is a real push. Additional funding is welcome, and may help to prevent the rate of decline, but quite a bit more money is needed in order to really re-vitalise the UK armed forces. It’s also worth mentioning that of the Defence budget the UK has, the numbers are a little bit cooked. For example MoD pensions are included in the UK Defence budget and constitute 10% of the spend. If this money was taxonomised outside of the defence budget, then that’s 10% more money to go on …. defence.
Exactly what the right moves to make are with the budget, given the UK’s other economic goals, and goals around improving public infrastructure, and what the right Defence strategy is for investing that money and building UK capabilities is way beyond the scope of anything I’m doing here.
Some Thoughts about Finding Money and Media Cycle Rhetoric on how “easily” that can be done…
One place you might think some easy money can be found is from scrapping silly government projects if they exist.
It has been alleged (though the government has denied it) that part of a deal to give away The Chagos Islands to Mauritius would involve billions of pounds in government spending28.
If a deal like this does exist, then clearly it is in the best interest of Britain for that money to go instead on defence. — however, I don’t know how reliable reports of these numbers in deals with Mauritius are given the government has denied them.
Im sure that whatever is actually going on with the Chagos islands is pretty complex. Currently there is a US military base on the islands, I don’t know if Starmer is signalling his intent to sell as a diplomatic bargaining chip with the US. I don’t know how much money is actually being suggested in negotiations with Mauritius. I don’t know why the UK government is so committed to selling them — there could be any number of secret reasons why it makes sense to do so. I also don’t know why the Labour government won’t be transparent about the actual numbers that have been suggested in talks with Mauritius. This whole topic is a black box, and I don’t think anyone other than Kier Starmer has a good idea of what’s really going on.
Not that that would stop a US politician with little information chiming in in the most toxic way possible, with Nigel Farage and other opportunistic idiots jumping in on the headlines!
Another suggestion for finding some easy money has come from Conservative political commentator Andrew Neil, stating “We CAN pay for a rapid rebuild of our military might - by using the hundreds of billions Miliband is planning to splurge on his fatuous pursuit of Net Zero”29.
I think this view is also mistaken, as Milliband's project with GB Energy is a vital part of our defence, making us energy independent and providing crucial energy infrastructure required for robust and resilient defence and manufacturing industries.
Additionally, Net Zero is currently a really valuable part of the UK’s modern economy
Think going green is just a nice idea? Think again. The net zero economy has become a powerhouse of job creation and economic expansion with 10.1% growth in the total economic value supported by the net zero economy since 2023. In 2024, there were 22,800 net zero businesses, with small and medium-sized enterprises (SMEs) making up 94% of the sector. Together, these businesses have pumped £28.8 billion into the economy - 0.82 billion less than the entire size of Wales's economy. They also support 273,000 full-time jobs, outpacing employment in the telecommunications industry.
And that's just the tip of the iceberg. When you factor in supply chain activities, the sector's economic impact skyrockets to £83.1 billion, supporting nearly 951,000 jobs across the UK - that's 2.9% of total UK employment. Even better, net zero jobs are 40% more productive than the national average, with wages 15% higher than the UK norm. In other words, these aren't just more jobs - they're better jobs.30
People seem to have lots of vibes based ideas that net-zero is inimical to productivity and enterprise, but the reality is that there is now a lot of empirical data showing that theres all these jobs and industries around net-zero and they have a whole host of benefits even including cheaper energy (not to say energy prices aren’t super expensive, just that the counter-factual where we didn’t have offshore wind things are much much worse) — for example, the UK’s ability to generate offshore wind power is enormous!31
Neil’s suggestion here seems more motivated by ideological opposition to climate change policy and years of related political talking points rather than up to date empirical data. I think it’s clear that Neil’s suggestions here would go agains the UK’s defence and economic goals. For example, how are we going to meet the energy requirements for data centres and big tech companies or the defence industry if we scrap proposals to improve our energy infrastructure at this point? What would the impact of that be on the UK economy and revenue raised through taxation to fund defence?
Do I have any useful suggestions here? No. I don’t know what the solutions are in terms of finding the money or balancing the budget. Im also not an economist or a professional politician. I also don’t think there are easy choices. I can’t recommend how this can be done. I wanted to highlight some of the complexities to lower the tone of debate where people think there are easy suggestions and simply want to lay into Rachel Reeves — this is not a clear cut problem with easy solutions — especially given the UK’s current tax burden.
With respect to defence, it’s clear that the UK needs to be spending more. We should be following European nations like Denmark32 and Poland who are happily pushing above 3% GDP on defence, immediately — particularly given the current geopolitical climate. i.e. German Chancellor Merz after winning the German elections
"I would not have believed that I would ever have to say something like this on a television program, but after Donald Trump's statements last week, it is clear that the Americans—at least this part of the American government—are largely indifferent to Europe's fate. I am very curious to see how we approach the NATO summit at the end of June—whether we will still be able to speak of NATO in its current form or whether we will have to establish an independent European defense capability much sooner. This is my absolute priority, and I have no illusions about what is happening in America. Just look at the recent days and how Elon Musk has intervened in the German election campaign—an unprecedented event. The interventions from Washington have been no less dramatic, drastic, and ultimately outrageous than those we have seen from Moscow. We are under massive pressure from both sides, which is why my absolute priority now is to establish unity in Europe."33
Given the UK's historical and present role in championing democratic values, both in Europe and globally, it is crucial we take decisive action and inspire others to follow—demonstrating the UK's unwavering commitment to defending democracy, opposing military aggression, supporting Ukraine's sovereignty, and strengthening the international rules-based order. This would reinforce Britain's position as a key player in maintaining global security and stability.
https://en.m.wikipedia.org/wiki/2015_Russian_Sukhoi_Su-24_shootdown
Turkey will save the day
Minor clarification - the trade numbers at the beginning are for goods and services. More than half of UK exports are services, and in particular it's two thirds to the US. So most of that £180bn exports to the US isn't being transported in a container.
Although it probably is going through those undersea cables.