The Under Secretary of War for Research and Engineering (USW(R&E)) serves as the primary advisor to Department of War (DoW) leadership on all matters pertaining to the Department's Research and Engineering (R&E) enterprise, technology development and transition, developmental prototyping, experimentation, and administration of testing ranges and activities. USW(R&E) has the lead responsibility within the Department for synchronizing Science & Technology (S&T) efforts across the DoW, the Joint Staff and the Services.

The USW(R&E) also serves as the Chief Technology Officer (CTO) of the Department and is tasked with the imperative mission of ensuring continuous advancement of technology and innovation within the DoW enterprise. As the CTO, the USW(R&E) advises the Secretary of War on all matters related to research; engineering; manufacturing; developmental test and evaluation; and technology development, innovation, and protection activities and programs in the DoW and occurring internationally. The USW(R&E) also establishes priorities across those matters to ensure conformance with Office of the Secretary of Defense's policy and guidance.

The USW(R&E) also has the oversight lead for critical capabilities managed by defense agencies and field activities including the Defense Advanced Research Projects Agency (DARPA), Missile Defense Agency (MDA), and Space Development Agency (SDA) as well as the Defense Science and Innovation Board offices.