The U.S. Navy Blue Angels flight demonstration team performs a flyover above the Lincoln Memorial during Independence Day celebrations on July 4 on the National Mall in Washington, D.C..
Acting Secretary of Defense Patrick Shanahan listens as President Trump speaks during a signing event for "Space Policy Directive 4" in the Oval Office of the White House in February.
Acting Secretary of Defense Patrick Shanahan was cleared by the Pentagon's Inspector General of allegations of ethics violations. Shanahan is seen here testifying at a House Armed Services Committee hearing last month.
Drew Angerer/Getty Images
Members of the U.S. military install multiple tiers of concertina wire along the banks of the Rio Grande near the Juarez-Lincoln Bridge at the U.S.-Mexico border in Laredo, Texas, in November.
Defense Secretary Jim Mattis announced his resignation on Thursday, following a decision by President Trump to withdraw American troops from Syria. He'll be replaced by Deputy Secretary of Defense Patrick Shanahan starting in January.
A border protection officer stands next to a recently upgraded section of fencing at the U.S.-Mexico border in Calexico, Calif., on Friday. The Pentagon says it will send 5,000 U.S. troops to the border.
Mark Ralston/AFP/Getty Images
The Pentagon only recently made cybersecurity a priority, the Government Accountability Office says in a new report, which found vulnerabilities in weapons that are under development.
Defense Secretary Jim Mattis speaks at the Pentagon Monday. The military received a big boost in funding last week, raising the overall budget to $700 billion this year.
The Bastille Day festivities in Paris last summer gave President Trump the inspiration to call for a military parade in Washington. But the Pentagon says there will be no tanks in its parade in November.