Key Takeaways:

- AI-driven technologies—such as generative AI, automated attacks, deepfakes, and drone–autonomous weapon integration—are rapidly transforming cyberspace into a complex arena of national security risk. Incidents in 2025 and the cyber dimension of the Russia–Ukraine war highlight that cyberspace has become a “fifth domain of warfare,” revealing the limitations of perimeter-based security models. In this evolving environment, the U.S. adoption of Zero Trust reflects a strategic shift toward assuming breach and reinforcing resilience amid intensifying geopolitical competition.

- U.S. cybersecurity strategy has become increasingly proactive across successive administrations, culminating in the 2023 strategy that embeds Zero Trust across all policy domains. The Department of Defense operationalizes this approach through the CIO-led Portfolio Management Office, four strategic objectives, and a structured seven-pillar maturity model aimed at full implementation by 2027. This demonstrates that Zero Trust is not a technical upgrade but a strategic reconfiguration of defense operations requiring cultural, procedural, and technological transformation.

- South Korea has begun adopting Zero Trust through guidelines, pilot programs, and national strategy integration, but practical challenges persist, including insufficient standards, limited interoperability, and resource constraints. As the U.S. raises expectations for allied cybersecurity maturity, Zero Trust becomes essential for interoperability in ROK–U.S. combined operations. South Korea must therefore institutionalize enforcement mechanisms, expand public–private pilots, build a standards-based ecosystem, and prepare defense systems for phased transition to establish Zero Trust as a sustainable national capability.

The rapid advancement of artificial intelligence is expanding the scale and functional importance of cyberspace at an unprecedented pace. Emerging technologies—such as generative AI, automated attack tools, hyper-realistic deepfakes, and the fusion of drones with autonomous weapons systems—are fundamentally altering the nature and trajectory of cyber threats. These developments extend far beyond conventional digital intrusions, creating complex and multidimensional risks to national security. Incidents in 2025, including major breaches of telecommunications infrastructure, illicit attempts to compromise domestic and international virtual asset platforms, and coordinated attacks on global Bitcoin systems, exemplify this accelerating transformation. Moreover, the cyber dimension of the Russia–Ukraine war demonstrated that cyberspace has firmly emerged as a “fifth domain of warfare,” complementing land, sea, air, and space. The conflict revealed the structural limitations of perimeter-based security models when confronted with persistent, asymmetric, and rapidly evolving threats. [[1]]

Against this backdrop, the United States’ adoption of Zero Trust as a core framework for national cybersecurity reflects more than a technical adjustment; it represents a strategic commitment to building a secure and resilient cyber environment in the face of rapidly shifting technological ecosystems driven by AI, cloud computing, and distributed operations. Furthermore, as cyber operations become closely intertwined with geopolitical competition, the recognition that security architectures must assume breach rather than rely on perimeter defense has gained global traction, reinforcing the strategic legitimacy and urgency of Zero Trust adoption. This shift underscores the reality that cyberspace is no longer a passive operational domain but an arena in which states compete for strategic influence, technological advantage, and operational superiority.

U.S. cybersecurity strategy has evolved in increasingly proactive and structured directions across the Bush, Trump, and Biden administrations. The Bush administration formally elevated cybersecurity to a national priority through the first National Strategy to Secure Cyberspace, while the Trump administration’s 2018 National Cyber Strategy introduced more assertive measures aimed at deterring malicious actors and strengthening collaboration with the private sector. Building on this trajectory, the Biden administration’s 2023 National Cybersecurity Strategy articulated five strategic pillars: protecting critical infrastructure, disrupting threat actors, shaping market forces, investing in future technologies, and strengthening international partnerships. At the center of this strategy lies the integration of Zero Trust principles across all policy domains, with the aim of modernizing federal IT and security infrastructures and establishing interoperable cybersecurity baselines for government entities, industry partners, and allied nations. [[2]]

The strategy also emphasizes a structural redistribution of security responsibility across the digital ecosystem, extending obligations to software suppliers, cloud service providers, and critical infrastructure operators. Under the current Trump administration, this Zero Trust–centric posture has been sustained—and in some areas intensified—with heightened expectations for cybersecurity maturity among allied nations. Such continuity reflects a bipartisan understanding within the United States that traditional defense models are no longer sufficient and that structural transformation is required to sustain national resilience and technological superiority. This bipartisan consensus is particularly notable given the partisan divides that characterize other areas of U.S. national security policy, suggesting that cyber resilience has emerged as a rare area of enduring strategic alignment.

The U.S. Department of Defense (DoD) plays a central role in operationalizing national strategy and views Zero Trust as a foundational capability for both cyber offense and defense. To coordinate implementation, the DoD established a Portfolio Management Office (PfMO) under the Chief Information Officer. This organization is responsible for integrating policy, technology, and organizational processes across the Department. It advances four strategic objectives: institutionalizing Zero Trust culture, securing and defending DoD information systems, accelerating the adoption of enabling technologies, and strengthening execution support. [[3]]  These objectives reflect the recognition that Zero Trust maturity cannot be achieved solely through technical enhancements; rather, it requires comprehensive transformation in organizational culture, operational procedures, and workforce behavior. In particular, the DoD acknowledges that sustaining Zero Trust over time necessitates continuous training, adaptive policy frameworks, and persistent evaluation mechanisms that evolve with emerging threats.

The DoD operationalizes Zero Trust through a structured maturity model built around seven pillars—encompassing users, devices, networks, applications, workloads, and data—each containing detailed capability requirements. [[4]]  The Department is pursuing a roadmap to achieve full Zero Trust implementation across all components by 2027. Importantly, this roadmap functions not merely as a timeline but as a strategic mechanism aligning budget planning, technology acquisition, workforce development, and operational execution under a unified security baseline. This demonstrates that Zero Trust is not a collection of tools, but a strategic architecture aimed at reconfiguring the operational foundation of national defense. The DoD’s gradual, mission-sensitive approach provides a valuable model for environments where operational continuity is critical and offers practical insights for other governments and organizations seeking similar transformation. Moreover, the DoD’s experience illustrates how institutional leadership and governance structures can accelerate adoption by reducing fragmentation and promoting coherence across diverse operational units.

South Korea entered the initial phase of Zero Trust adoption with the release of government guidelines in 2023, followed by Guideline 2.0 in 2024, pilot programs, and formal incorporation into the National Cybersecurity Strategy. [[5]]  These measures expanded the institutional foundation for adoption. However, significant practical challenges remain, including insufficient specificity in the guidelines, lack of domestic technical standards and interoperability frameworks, and constraints in budget and skilled personnel. Such obstacles indicate that South Korea’s current efforts remain at a foundational stage and that deeper institutionalization is necessary for Zero Trust to drive substantial change in national security posture. The Korean case illustrates the broader challenge faced by many states: translating conceptual alignment with Zero Trust principles into operational and measurable outcomes.

Additionally, the United States is increasingly raising cybersecurity expectations for its allies, positioning Zero Trust not merely as a domestic modernization initiative but as a strategic requirement for ensuring interoperability in combined-operations environments. Because ROK–U.S. combined operations rely on tightly integrated command-and-control, intelligence, surveillance, reconnaissance, and military communications systems, discrepancies in security architecture could create operational vulnerabilities or degrade mission effectiveness. These dynamic highlight the growing interdependence of alliance cybersecurity, where the resilience of one partner directly affects the operational effectiveness of the other.

If Zero Trust requirements expand into these mission-critical systems, South Korea will need to prepare a phased transition roadmap and ensure technical compatibility. Zero Trust should thus be reconceptualized as a core pillar of South Korea’s national security strategy rather than as an isolated policy project or set of technical controls. This requires institutionalizing guideline enforcement mechanisms, expanding joint public–private pilot programs, building a standards-based domestic technology ecosystem, and preparing defense systems for gradual transformation in alignment with combined-operations requirements. Because Zero Trust encompasses technological, organizational, policy, and international cooperation dimensions, South Korea must develop a sustainable national implementation framework capable of integrating these elements.

In conclusion, Zero Trust has emerged as a strategic architecture that bridges national security objectives with technological modernization. The U.S. experience demonstrates that dedicated organizational structures, phased roadmaps, standardized capability models, and integrated policy–technology approaches can significantly enhance national cyber resilience and operational superiority. For South Korea, redefining the strategic significance of Zero Trust and establishing a durable, execution-oriented implementation framework will be essential to achieving both national security and technological competitiveness in an increasingly volatile global threat landscape. Ultimately, successful Zero Trust adoption will depend on sustained political commitment, resource investment, and cross-sector collaboration, ensuring that cybersecurity evolves from a reactive policy domain into a persistent and mature national capability.