Defense Primer: Under Secretary of Defense for Research and Engineering [Updated February 4, 2020] [open pdf - 491KB]
From the Document: "Advances in science and technology have long played a critical role in ensuring the technological preeminence of the United States military. For this reason, the Department of Defense (DOD) is the largest funder of federal research and development. The Under Secretary of Defense for Research and Engineering (USD (R&E)) is a civilian official reporting directly to the Secretary of Defense. The USD (R&E) serves as the principal advisor to the Secretary of Defense for DOD research, engineering, and technology development activities and programs. Over the last several years, policymakers and others have expressed concern that the long-held technological edge of the U.S. military is eroding due, in part, to the proliferation of technologies outside the defense sector, organizational and cultural barriers to DOD effectively incorporating and exploiting commercial innovations, and insufficient engagement with leading-edge companies that have not historically been a part of the DOD innovation system. The establishment of the USD (R&E) as the fourth highest ranking DOD official--behind the Secretary, Deputy Secretary, and Chief Management Officer--was intended to promote faster innovation and to reduce risk-intolerance in the pursuit of new technologies."
CRS In Focus, IF10834
Congressional Research Service: https://crsreports.congress.gov/