General Mark Milley retires, takes a parting shot at ex-President Donald Trump.

Milley's ceremony highlights the military's political role during the Trump era.

Without naming Trump, he criticizes service to a "wannabe dictator."

Air Force General Charles "CQ" Brown becomes the second African American in his role.

Milley's 40-year career includes handling Afghan withdrawal and supporting Ukraine.

His tenure saw the military in political controversies.

Milley privately reassured China during post-election chaos, angering Trump.

Trump's threats led to increased security measures for Milley.

Biden condemns Trump's remarks and Republican silence.

Brown, an experienced pilot, succeeds Milley.