The Department of War (DOW) stands at a critical juncture, grappling with the dual pressures of accelerating technological change and evolving threats, all while navigating constrained resources. The Modular Open Systems Approach (MOSA) emerges as a strategic imperative, offering a decisive path forward to maintain battlefield dominance amid these challenges. This is not merely a design preference but a fundamental shift in how the DOW must approach defence technology to ensure future readiness, adaptability, and resilience.
At its core, MOSA is built around modular components, open standards, and clearly defined subsystem boundaries. This architecture allows hardware and software components to be added, removed, or upgraded independently, eliminating the need for full system redesigns. The result is a more agile, cost-effective, and interoperable defence infrastructure. As emphasized in recent DOW modernization guidance, MOSA is not just about engineering—it’s about operational advantage. It empowers the DOW to move faster, spend smarter, and stay ahead of adversaries in an era defined by technological disruption.
Several converging trends underscore the urgency of adopting MOSA. First, adversaries are rapidly advancing their capabilities across all domains, from cyber warfare to hypersonic missiles. To counter these threats, the DOW must ensure its systems are upgradeable and adaptable. Closed, monolithic systems, which are slow to evolve, will quickly become obsolete. MOSA systems, by contrast, reduce development cycles and enable faster technology insertion, giving the DOW a critical edge.
Second, budgetary pressures and cost constraints demand a more efficient approach to defence spending. Proprietary components, unique interfaces, and vendor lock-in drive up lifecycle costs. Open architectures, on the other hand, encourage competition among suppliers, reduce reliance on single vendors, and enable rapid upgrades without costly redesigns.
Third, the Joint All-Domain Command and Control (JADC2) initiative underscores the need for seamless interoperability across services and allies. Open standards and interfaces accelerate integration, enabling real-time collaboration and data sharing across air, land, sea, space, and cyber domains. This is essential for effective C5ISR (Command, Control, Communications, Computers, Cyber, Intelligence, Surveillance, and Reconnaissance) operations.
Finally, rapid sustainment and upgrades are critical. Systems must be maintained and modernized over decades, and open architectures allow individual modules to be updated or replaced without overhauling the entire system. This approach fosters a more diverse industrial base, ensuring long-term sustainability and innovation.
However, implementing MOSA is not without challenges. Standards governance and conformance must be carefully managed to ensure true interoperability among modules. Open standards must be collaboratively developed, rigorously enforced, and continuously refined. Early planning and consistent coordination across programs are essential to fully realize the benefits of MOSA.
Intellectual property (IP) and data rights must also be carefully balanced. Industry’s IP can be safeguarded up to the interface boundary, preserving the DOW’s ability to operate, maintain, and upgrade systems without excessive royalties or restrictive licensing barriers.
Legacy systems integration presents another hurdle. Much of the DOW’s infrastructure is outdated, and migrating or integrating with older systems can be complex and costly. Transitioning to MOSA must be a priority in each acquisition roadmap, with incentives given to vendors who adopt this architecture.
Cybersecurity risks are also a concern. Published interfaces and standards invite attacks, and rigorous security architecture within individual components is essential. Continuous modification to platforms and systems makes it harder for adversaries to identify exploitable weaknesses, but robust cybersecurity measures must remain a priority.
Cultural and contractual inertia within the defence industry poses a final challenge. Many emerging neo-defence tech firms and startups are built around proprietary solutions that drive exclusivity to reduce future competition. It will take successful program examples to demonstrate how both industry and the DOW can benefit from open architectures.
Certification, testing, and validation are also critical. Modular systems and plug-and-play components require robust certification frameworks, particularly in safety-critical or mission-critical systems. Simplifying and democratizing access to government test labs and certification capabilities will be key to validating conformance, interoperability, and security of modules and components.
The DOW has already begun codifying MOSA into acquisition policy and law for major defence programs. The Army’s Enduring High Energy Laser and the C4ISR/EW Modular Open Suite of Standards exemplify this forward-thinking approach to modular and interoperable system design. These initiatives reflect a broader shift in the DOW’s acquisition, engineering, and sustainment paradigms, aligning them with the realities of fast-moving threat environments, stretched resources, and the accelerating pace of technology.
In embracing open systems, the DOW can ensure its platforms, weapons, and software remain relevant, competitive, upgradeable, and interoperable—not only today, but for