What the 2025 Strategic Defense Review Means for US-UK Strategic Cooperation: A Discussion by CSIS
- Mischa Khanna
- Aug 6
- 3 min read
On July 30, 2025, the Center for Strategic and International Studies (CSIS) hosted a discussion on developments in the US-UK strategic cooperation, since the release of the United Kingdom’s updated Strategic Defense Review (SDR) published on June 2, 2025. Featured in this event were Dr. Heather Williams, Director of the CSIS Project on Nuclear Issues, Dr. Tom Karako, Director of the CSIS Missile Defense Project, and Dr. Kari A. Bingen, Director of the CSIS Aerospace Security project. The core argument of this review is the UK is leaning into a long-term leadership role within NATO, taking on deterrence and defense innovation.
F-35A Procurement: More than Symbolism?
Prime Minister Starmer announced the UK would procure at least 12 F-35A fighter jets. This announcement was made at the NATO Summit in June, shortly after the Strategic Defense Review. Dr. Heather Williams describes this step as a “historic moment” marking it as a revival of the UK’s nuclear-capable air leg, which has been absent from the British defense policy. Prior to recent years, Britain’s Labour Party had distanced itself from nuclear delivery and leadership roles. However, it is now apparent the UK is fully committing to the nuclear-sharing mission within NATO and intends to take on a leadership role as a primary deterrent. Dr. Williams emphasizes this movement is not just symbolic, but rather a strategic response to the shifting realities and uncertainties, acknowledging Russia as a potential threat.
Three Domains of Modern Defense
The CSIS discussion emphasized the three interconnected domains of modern defense: hardware, software, and cognitive domains.
Domain | Focus Areas | Key Examples | Strategic Importance |
Hardware | Physical military assets and platforms | F-35A jets, ISR satellites, missile tracking systems, autonomous drones | Enables kinetic force projection, enhances deterrence posture |
Software | Digital systems, data infrastructure, AI | Digital targeting networks, cybersecurity layers, algorithmic decision tools | Increases operational precision, survivability, and interoperability |
Cognitive | Psychological resilience and information war | National resistance strategies, NGO & think tank public education initiatives | Shields public trust, counters disinformation, supports morale |
As defense competition expands into non-kinetic and non-physical realms, this tri-domain framework underscores the need for integrated policy responses, emphasizing that software and cognitive resilience are as essential as physical force in modern deterrence.
Strengthening NATO Resilience Across all Domains
Beyond aircraft procurement, the SDR emphasized a greater, united approach to security. Dr. Bingen emphasized that space is no longer a peripheral domain. Adversaries are developing capabilities to combat Intelligence, Surveillance, and Reconnaissance (ISR) architecture. Dr. Bingen highlights that in response, plans have been outlined in the SDR to improve upon the UK's long-duration satellite coverage that enables early missile warning, tracking, and precision, both strengthening the UK’s defense and NATO’s joint force.
Dr. Bingen and Williams also noted the uncrewed aerial systems as a rapidly evolving capability. Dr. Bingen pointed out the importance of drone systems in operations. Included in the SDR is the commitment to developing and deploying autonomous systems, reflecting the shift to tech-driven operations. Bingen applauds the British creative approach to the Latvian collaboration on counter-drone testing and development.
A Deepening Alliance: The U.S and UK
Despite the UK’s growing commitments and national investments, Dr. Williams emphasized that the US–UK relationship remains the bedrock of the UK’s nuclear deterrent strategy. The UK continues to rely on US technical support, intelligence integration, and NATO planning structures to sustain its deterrent credibility. Both Dr. Bingen and Dr. Williams reinforced the point that no European nation, including the UK, can substitute the dominant strategic role the U.S. plays in NATO’s nuclear policy.
Rather than replacing the U.S., the UK’s role is to fill capability gaps, share burdens, and signal its political will to lead where appropriate. The SDR, when viewed alongside the F-35A announcement, demonstrates a broader British effort to transform from a supporting actor to a capable, proactive stakeholder in NATO’s deterrence ecosystem. The discussion concluded that these efforts, while rooted in national strategy, are fundamentally aligned with broader alliance resilience goals, and will be critical to ensuring NATO’s technological and strategic edge amid a rapidly evolving threat environment.
Sources:
CSIS. 2025. “U.S.-UK Strategic Cooperation.” CSIS, July 30. Accessed July 30, 2025.
