U.S. President Donald Trump has named Deputy Defense Secretary Patrick Shanahan as acting defense secretary.
In a post on Twitter on December 23, Trump described Shanahan as "very talented" and said the appointment was effective as of January 1.
Shanahan replaces Defense Secretary Jim Mattis, who resigned on December 20 over Trump's decision to withdraw all U.S. forces from Syria. Mattis had said that he would continue serving until the end of February to facilitate a smooth transition.
Shanahan, a mechanical engineer by education, is a former senior vice president for U.S. aircraft manufacturer Boeing.