Christopher Miller has stepped into a role that has been empty for months in the Pentagon. The Deputy Assistant Secretary of Defense for Special Operations and Combating Terrorism position was emptied in September when Andrew Knaggs left the role to run as the Republican challenger for House seat in Richmond, VA. Miller’s new position involves checking and advising military actions with consideration to the possible outcomes and consequences. This comes in time with other officials announcing their leave in January, such as the head of DARPA and chief of staff to Defense Secretary Mark Esper.
Source: https://breakingdefense.com/2020/01/more-officials-leave-pentagon