Donald Trump has fired defence secretary Mark Esper and replaced him with counterterrorism head Christopher Miller.
Mr Esper was confirmed as defence secretary in July 2019 but had clashed with the president this year.
Mr Miller, director of the National Counterterrorism Centre, takes over the role until Joe Biden enters the White House in the new year.
Presidents who win re-election often replace cabinet members but losing incumbents have previously kept their Pentagon chiefs in place until Inauguration Day to preserve stability in the name of national security.
Mr Trump thanked Mr Esper for his service and said Mr Miller will do “a great job”.
