DoD’s Shifting Homeland Defense Mission Could Undermine the Military’s Lethality

Melissa Dalton CSIS April 22, 2025

Senior Adviser (Non-resident), Defense Budget Analysis and Aerospace Security Project, CSIS

The Trump administration’s issuance of the executive order on an Iron Dome for America (now called Golden Dome), along with its emphasis on the Department of Defense’s (DoD) role in border security, marks a significant shift in U.S. defense strategy, the domestic use of the military, and the capabilities and resources allocated to these missions and activities, with implications for the overall health of U.S. civil-military relations. In fact, the associated costs and trade-offs could lead to inefficient use of taxpayer dollars and undermine the administration’s own stated priority of improving the military’s lethality.

Moreover, putting the U.S. military centrally into a border security role increases risks to service members who are not trained or equipped for this mission. While DoD has not released full details of the recent vehicle accident in New Mexico that killed two Marines and seriously injured another, the incident raises important questions about why Marines were performing this task instead of law enforcement agents and whether they had the appropriate training and equipment to conduct the task safely. 

Overall, such a dramatic shift in homeland defense merits congressional oversight in the review of the administration’s interim strategic guidance, the forthcoming 2026 National Defense Strategy, and the submission of the FY 2026 budget, to assess trade-offs with other priorities vital to strengthening the military’s lethality. The administration and Congress should closely examine the affordability of Golden Dome—including its phasing, pace, and required level of investment—relative to other priorities, and review the trade-offs for modernization and readiness. Finally, the administration and Congress should fully resource the Department of Homeland Security (DHS) and other agencies with the statutory lead, expertise, and experience for the border security mission.