"I want to thank General Charles 'CQ' Brown for over 40 years of service to our country" says Trump in a statement where he describes the air force general and former fighter pilot as a gentleman and outstanding leader.
The new US Defense Minister Pete Hegseth demanded in a podcast in November, before his appointment as minister, that Brown must go. Hegseth has also, in one of his books, wondered if it's the case that Brown got the job because he is black. One of Trump's and Hegseth's political priorities is to end all plans, programs, and efforts for diversity and inclusion.
As a replacement, Trump nominates Dan Caine, lieutenant general in the air force and former fighter pilot, but most recently deputy chief for military affairs at the intelligence agency CIA. Caine does not have the qualifications required by law for the new role, something the president can, however, make an exception from if it is in the nation's interest.
As chairman of the council for defense branches, the primary task is to function as an advisor to the president, the White House, and the defense minister. They should not need to turn to the army, air force, or navy individually, for example, to get the military's view on current issues. The role does not entail any formal, military decision-making power.