The United States has seen its technological edge erode as other nations caught up while the U.S. was preoccupied with counter-insurgency. Of equal concern to Alan Shaffer, the Pentagon's principal deputy assistant secretary for research and engineering, is that "the DoD has lost 10,000 scientists and engineers since 2011." Also, beginning in 2013, the average age of DoD S&Es started to climb. See his and other R&D officials testimony.
Source: Department of Defense congressional testimony.