Choose your own DIP adventure

Build Britain's defence on £750bn

You hold the pen on the Defence Investment Plan. Ten years, one budget, and every pound spent on one capability is a pound denied another. The deterrent is ringfenced. The Treasury is circling. The threats, regrettably, are not waiting for the next review. Choose.

OFFICIAL-SENSITIVE · Annex affordability

Ministerial confidence:

Reprofile before reading

BRIEF Allocate the 2026–2035 defence budget across 14 capability areas RULE Balance the books — or explain the black hole to the Chancellor TEST Three crises, eight newspapers and Sir Humphrey will judge the force you bought

Set the funding line

The Strategic Defence Review of June 2025 was costed against a rising line: 2.5% of GDP by 2027, then 3% in the next Parliament. NATO has since set a new 5% Hague benchmark for 2035 — 3.5% core defence plus 1.5% defence-and-security-related spending. The capability bill, meanwhile, is fixed at roughly £750bn over the decade. Pick your line — and watch how much of the plan it actually pays for.

— AND A STRATEGY

Money is only half the plan. The same envelope builds a very different force depending on the fight you are planning for. Your posture decides how the final verdict weighs your choices — and which contingency becomes the main effort.

Posture changes how the plan is judged; the sliders change the force you are actually buying.

Choose the accounting universe

The same force looks different under Treasury optimism, NAO pessimism or crisis inflation. This does not replace the scoring model; it changes the fiscal penalty and the warnings so readers can see how assumptions move the answer.

Draw up the plan

Funding health:starvedleanfundedheavy│ = requirement

Capability area — modelled 10-year allocationAllocation scale£bn / vs req.

Modelled ORBAT — what this plan roughly buys

updates when sliders or presets change · UK today + France

These are deliberately rough translations from money into force structure. They are not an MoD shopping list. They update when the allocations change; posture changes how the plan is judged, but spending changes the force. Low funding does not merely stop new purchases: it also erodes upgrades, crews, spares and industrial cadence. The cards are there to show the difference between owning things, crewing them and sustaining them. The French comparison is affectionate, accurate enough for context, and included because civilisation requires a benchmark and a rival.

Owned
the modelled force structure the money buys on paper.

Available
owned force after people, maintenance, estate and logistics have bitten.

Sustained
available force after munitions, spares and endurance are tested.

The decade profile — when the money lands

III

The verdict

Grade

Assessment

Consequences on the ground

Stress test the force

Plans are easy on paper. These are the three contingencies the SDR builds toward. Your allocation decides how the force performs in each.

How Britain compares

Share-of-GDP and absolute figures for allies are NATO/IISS estimates for 2024–25: Poland is the alliance's top spender by GDP share (~4.5%), the United States around 3.4%, with Germany, France and the UK clustered near 2–2.5%. Your figure is the implied 2035 core-defence share at your chosen funding line; NATO's Hague benchmark also includes a separate 1.5% defence-and-security-related pillar. Absolute UK spend is illustrative of the envelope, not a NATO-accounted total.

VII

Whitehall reacts

Overheard in the corridors, the clubs and the consultancies. Entirely fictional archetypes; any resemblance to a real Permanent Secretary is a coincidence they would strenuously deny.

VIII

MilTwitter reacts

Fictional composites, not actual quotes: the reply guys, logistics obsessives, anonymous procurement accounts and doctrinal newsletter writers who will find the weak seam before lunch.

Allies and adversaries react

Fictional diplomatic cables from people who have read the plan more carefully than ministers would prefer.

Fleet Street reacts

The morning after. A note on press freedom: these are fictional correspondents writing for parody mastheads — any resemblance to real Lobby hacks is entirely affectionate.

XIAssumptions labOpen the model: capability assumptions, public anchors and delivery risks.

Open the black box

This simulator is a structured argument, not an oracle. Each capability has a modelled ten-year requirement, a confidence rating, an official public anchor and a delivery risk. The anchors come from current public MoD accounts, the old Equipment Plan and official statistics; the capability splits are a transparent crosswalk, not a leaked DIP table. Underfunding hurts more than overfunding helps: a hollow force is easier to create than a brilliant one.

Scoring curve: below requirement, risk rises quickly; above requirement, returns diminish. Postures then reweight the same capabilities: a Euro-Atlantic plan rewards land, munitions, people and air defence; a Global Britain plan rewards maritime, combat air, space and R&D; a Homeland-first plan rewards air defence, cyber, space, drones and resilience.

Time matters: back-loaded plans are politically convenient and strategically dangerous. A pound in 2035 does not stop a missile in 2028, and a sudden submarine splurge does not conjure nuclear welders from the Solent.

Capability assumptions

XIISources deep diveUnroll the public data, context charts and source cards behind the simulator.

For readers who want to audit the plumbing. These are the public anchors behind the model; the allocation splits remain an editorial apportionment, not an official MoD table. Public data mostly tell us who spent the money and whether it was resource, capital, equipment or infrastructure; the simulator translates that into strategic capabilities.

How the model is calibrated

Known with reasonable confidence: the MoD's current organisational outturn, Equipment Plan and Infrastructure Plan outturn, staff costs, equipment-support costs, and the NAO's ten-year Equipment Plan affordability gap. Not public: a clean ten-year table for nuclear, SSN-AUKUS, surface fleet, combat air, munitions, drones, cyber, readiness and estate as capability buckets.

What this site does: it uses official public accounts and NAO figures as anchors, then makes a transparent modelled apportionment into 14 capability areas. The word requirement below means modelled requirement, not an official MoD allocation.

The NATO mountain, 2025 estimates

Defence expenditure as a share of GDP. The old 2% benchmark now looks like base camp; the Hague core-defence benchmark is 3.5%, with a wider 5% total including defence-and-security-related spending.

Polandfront-line spender

4.48%

Lithuaniaeastern flank

4.00%

United Statesglobal burden

3.22%

United KingdomNATO estimate

2.40%

Francemortal enemy*

2.05%

2%3.5% core5% total

Source: NATO Defence Expenditure of NATO Countries, 2014-2025. *Mortal enemy in the affectionate, Agincourt-to-AUKUS sense.

Britain's near-term cash line

Public spending plans rise in cash terms before the harder question begins: how to get from the Spending Review settlement to 3%, and then toward NATO's Hague world.

2024/25actual/outturn

£60.2bn

2025/26SR25 start

£62.2bn

2028/29planned

£73.5bn

2.5% by 20273% later

Source: House of Commons Library, UK defence spending, and the Strategic Defence Review 2025. Cash figures are context, not the simulator's ten-year envelope.

What current accounts actually reveal

MoD 2024-25 public accounts are strongest at organisational and accounting categories, not the simulator's strategic capability buckets. These figures are anchors for calibration, not sliders.

Total resource & capital outturnDefence Board-reviewed basis

£73.5bn

Equipment Plan outturnprocurement + support

£24.9bn

Staff costsarmed forces + civilians

£17.8bn

Infrastructure Plan outturnestate and capital works

£6.8bn

DNE Equipment Plan outturnnuclear enterprise

£7.6bn

Equipment supportgoods & services line

£6.9bn

Source: MoD Annual Report and Accounts 2024-25. Several lines overlap conceptually; they are shown as calibration anchors, not additive totals.

Data last checked: May 2026 · official figures move; procurement promises move faster

XIII

Glossary for normal people

Sources & method

The model. Fourteen capability areas each carry a fixed ten-year modelled requirement — this simulation's estimate of what the costed force actually needs — summing to roughly £750bn. The budget envelope varies with the GDP line you choose. At the SDR's own 3%-path funding the requirements just balance; hold spending near 2.6% and the requirements exceed the envelope by about £110bn, the affordability gap the National Audit Office has repeatedly flagged; move to NATO's Hague 5% benchmark and genuine headroom opens up. Each area scores on a saturating curve (diminishing returns above its requirement, sharply rising risk below it). Six capability dimensions are weighted blends of the areas; "allied standing" also rewards the ambition of the funding line itself.

The figures are grounded in: the Strategic Defence Review 2025 and the House of Commons & House of Lords Library briefings on it; the NAO Equipment Plan 2023–2033 (forecast cost £305.5bn vs £288.6bn budget; Defence Nuclear Enterprise £109.8bn; nuclear and naval the largest cost drivers); the 2025 Spending Review (defence £62.2bn in 2025/26 rising to £73.5bn by 2028/29); HM Treasury and MoD statements on the £15bn warhead programme, £6bn munitions commitment, up-to-£1bn homeland air-and-missile defence, the CyberEM Command and Digital Targeting Web; and published programme costs for Dreadnought (~£41bn lifetime), SSN-AUKUS (up to 12 boats), GCAP/Tempest (£16bn+ UK), and the Type 26 (~£1bn a hull) and Type 31 frigates. The model is calibrated against current public MoD accounts, the 2024-25 Equipment and Infrastructure Plan outturns, staff and support costs, UK equipment statistics and the NAO Equipment Plan; requirement splits are the author's transparent crosswalk from those public categories into strategic capabilities, not official MoD allocations.

What it is not. A planning tool. The scoring is a deliberately legible game model, designed to make real trade-offs visible — the crowding-out power of the ringfenced deterrent, the readiness cost of buying kit you cannot crew, the munitions lesson of Ukraine — not to predict outcomes. The actual Defence Investment Plan, repeatedly delayed through 2025, is the document this game anticipates.