July 2025
Issue brief The border and beyond:
Homeland defense in an era of new strategic threats
Clementine Starling-Daniels and Amy Cowley From launching cyberattacks to targeting critical infrastructure, US rivals are bringing the fight closer to home. Defending against these threats will require not just military might, but smarter defense planning, greater resilience, and military modernization.
Bottom lines up front •
The domestic systems that underpin US security and prosperity—including energy grids, digital and financial networks, the defense industrial base, and transportation infrastructure—are increasingly vulnerable to a broad spectrum of modern threats: conventional, nuclear, asymmetric, and digital. To address these persistent vulnerabilities, the Department of Defense (DoD)’s forthcoming National Defense Strategy (NDS) is expected to prioritize homeland defense.
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Responding to these complex threats requires a comprehensive approach to homeland defense that extends beyond border security. This approach must encompass missile defense and the protection of critical defense systems—such as space infrastructure—from cyberattacks and other forms of malign interference.
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In the NDS, the DoD must clearly define where it will take the lead and where it will support civilian agencies and the private sector. This includes reinforcing efforts to defend critical infrastructure and strategic nodes— such as energy grids, ports, digital systems, and industrial hubs—against cyber and physical attacks, long-range missile threats, and coercive economic activities.
Introduction Threats to the US homeland have fundamentally changed from two decades ago. In the years following 9/11, the most pressing dangers came from terrorist groups intent on carrying out attacks on US soil. Today’s threat landscape is broader and more complex. Peer-state competitors, transnational criminal organizations, and non-state actors now possess the means to target the
ATLANTIC COUNCIL
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US homeland through a range of kinetic and non-kinetic capabilities. These include long-range missiles, cyberattacks, sabotage, disinformation, and malign foreign influence—all tools designed to disrupt critical infrastructure, weaken public trust, and undermine the ability of the United States to project power abroad. The traditional model of homeland defense has relied on a layered approach of projec-