Army Secretary Mark T. Esper takes over on Sunday as the Trump administration's acting secretary of defense — the third defense chief for the administration and its first Republican. 
Acting Defense Secretary Patrick Shanahan has withdrawn from consideration to head the U.S. military, President Donald Trump announced on Tuesday, stoking uncertainty about the leadership of the Pentagon at a moment of rising tension with Iran. 
China conducted a flight test of its newest strategic submarine-launched missile, the JL-3, coinciding with the visit to Asia earlier this month by Acting Defense Secretary Patrick Shanahan. 
Secretary of Defense James Mattis announced Wednesday that the Pentagon was renaming U.S. Pacific Command to Indo-Pacific Command in order to better reflect regional priorities. 
Secretary of Defense James Mattis dismissed rumors Wednesday that he disagreed with President Donald Trump on the administration's decision to launch airstrikes on Syria. 
Secretary of Defense James Mattis dismissed reports that he's apprehensive about John Bolton joining the Trump administration, saying that he had "no reservations" about their ability to work together. 
Secretary of Defense James Mattis, often recognized for his memorable quips and being a tough-talking military leader, showcased a softer side in a note sent recently to U.S. Olympian Maddie Rooney. 
