Project CIRRUS: Moving Defence to the Cloud and Building the Digital Backbone

Overview

Every digital ambition the Ministry of Defence holds — from the Digital Targeting Web to AI-enabled decision-making, from real-time sensor fusion to predictive logistics — depends on one thing: a modern, secure, scalable cloud infrastructure. Without it, data remains locked in ageing data centres, applications cannot be modernised, and the promise of digital transformation stays on paper. Project CIRRUS is the programme charged with making it real.

CIRRUS serves as the MOD’s umbrella programme for migrating, rationalising and modernising cloud infrastructure across all security classifications — OFFICIAL, SECRET and TOP SECRET. It is not a single contract or platform but a portfolio of interconnected sub-programmes that together deliver unified, hyperscale cloud capabilities to Defence. These include Data Centre Rationalisation, which retires obsolescent on-premise infrastructure; Emporium, an application modernisation laboratory; the Digital Foundry, which drives AI and data innovation; and the MODCloud platform itself, which provides the production cloud services that Defence relies upon every day.

The scale of the task is considerable. By 2023, CIRRUS had already overseen the migration of over 400 workloads to cloud environments. But migration is only part of the story. CIRRUS is also modernising legacy applications, providing foundational infrastructure for AI, analytics, resilient storage, edge computing and secure cross-classification services, and ensuring that the MOD’s cloud estate integrates with allied platforms including those of the US Department of Defense, NATO and Five Eyes partners. In short, CIRRUS is building the digital plumbing upon which every other Defence digital programme depends.

Strategic Purpose and Objectives

The Foundation Beneath the Transformation

CIRRUS exists to deliver the cloud layer of the MOD’s Digital Backbone — the singular, secure, modern digital infrastructure that connects sensors, effectors and decision-makers across all domains. Without CIRRUS, programmes such as NEXUS, the Digital Targeting Web, Maritime Domain Awareness and Defence Intelligence cannot access the hyperscale computing, secure storage and data services they need to function. It is the programme that turns the Digital Backbone from an architectural concept into an operational reality.

The strategic value goes beyond technology. CIRRUS enables cost-effective, secure and interoperable access to digital tools for warfighters, defence teams and partners. It provides strategic advantage through rapid innovation, evergreen technologies and access to new cloud-native capabilities that would be impossible to deliver through legacy on-premise infrastructure. Its sub-programmes cohere cloud migration, application modernisation and tactical edge deployments, ensuring that the MOD’s cloud estate is not simply a replacement for data centres but a genuinely new way of delivering digital capability.

Integration with allied platforms is a critical dimension. CIRRUS ensures that the UK’s cloud infrastructure is interoperable with the cloud environments used by the US, NATO and Five Eyes, enabling coalition information sharing and joint operations at a level of speed and security that legacy systems could never achieve. In a world where allied interoperability is as important as sovereign capability, this integration is not optional — it is a strategic imperative.

Budget and Financial Structure

Programme Value

Investment in CIRRUS exceeds £600 million in confirmed contracts between 2020 and 2025. Notable awards include the £400 million Google sovereign cloud contract in 2025, a £17 million Microsoft Azure direct award in 2020–2022, £34 million for Data Centre Rationalisation consultancy from 2021, £211 million in cloud-related contracts between 2020 and 2023, and £7.773 million for cyber security services from 2023 to 2026. The actual portfolio cost is likely higher given foundational investments and the ongoing shift of the majority of compute expenditure to cloud. Defence Digital’s annual budget exceeds £2 billion.

Budget Division and Holder

MOD Defence Digital is the strategic owner and primary funder. Delivery is managed by the CIRRUS programme office, MODCloud teams, IT and data centre rationalisation teams, the Digital Foundry for innovation, and Emporium for application modernisation. Oversight is provided by the MOD Chief Information Officer and Digital Functional Lead. Specific contract management for Google, Microsoft, AWS, Oracle and other providers sits with Defence Digital’s commercial division, with oversight from MODCloud, DCR and innovation team leads.

Procurement and Acquisition

Acquisition Pipeline

CIRRUS appears in the MOD Acquisition Pipeline under Defence Digital cloud transformation programmes, covering Data Centre Rationalisation, MODCloud, hyperscale frameworks, secret and sovereign cloud projects, and innovation and migration services. Major procurement runs through the Defence Sourcing Portal and Crown Commercial Service frameworks including G-Cloud, Cloud Compute 2, TS3, DOS and Cyber Security Services 3.

Tender Information

The landmark Google sovereign cloud contract was awarded in September 2025 at a value of £400 million. The Azure direct award followed in June 2020 at £17 million, and the DCR consultancy award in November 2021 at £34 million. Ongoing migration and new awards for secret, hybrid and tactical edge cloud capabilities continue through 2024–2026, including contracts under Cloud Compute 2 and bespoke sovereign frameworks for the UK MOD and its allies. Tender references are held within the Defence Sourcing Portal and CCS framework documentation.

Why It Matters

CIRRUS is the programme that makes every other Defence digital initiative possible. Without modern, secure, scalable cloud infrastructure, the MOD cannot deliver the Digital Targeting Web, cannot field AI at scale, cannot provide real-time data to commanders and cannot integrate with allies at the speed that modern operations demand. It is, in the truest sense, foundational — the invisible layer upon which the visible transformation of UK Defence depends.

The programme also represents a fundamental shift in how Defence consumes technology. By moving from bespoke, on-premise data centres to multi-vendor, hyperscale cloud, the MOD gains access to continuous innovation, evergreen security and elastic computing capacity that can scale with operational demand. That shift is not just a technical upgrade — it is a cultural and organisational transformation that touches every part of Defence.

For industry, CIRRUS offers sustained and growing opportunity across cloud services, data centre migration, application modernisation, cybersecurity, edge computing and sovereign cloud solutions. The £400 million Google contract demonstrates the scale of individual awards, while the multi-vendor, framework-driven procurement approach ensures that opportunities are not confined to a single provider. Companies with expertise in hyperscale cloud, secure multi-classification environments, application migration, AI infrastructure and tactical edge computing will find CIRRUS and its associated programmes among the most significant addressable markets in UK defence technology.

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