He described former Defense Secretary Jim Mattis as "the world's most overrated general" during a meeting on Syria.
"We have to always be concerned with this," the former defense secretary said.
Officials said F/A-18 E/F Super Hornet and EA-18G Growler fleets each "stand above" the 80% readiness goal.
Former Defense Secretary Jim Mattis also said Afghanistan needs more "resources" following the collapse of peace talks.
Former Defense Secretary and Marine Gen. James Mattis joined a business advisory group.
The former SecDef had ordered the F-16, F-22, F-35 and F-18 fleets brought to 80 percent mission capable rates.
The book is styled as a three-part course in leadership tracing Mattis' 40-year career.
The former defense secretary said more leadership guidance is necessary for the change to be implemented.
"We're going to have to learn from our past," he said, pointing to the rise of ISIS when U.S. troops pulled out of Iraq.
The suspect in two killings allegedly sought revenge for being sidelined from cases challenging the male-only draft.
Sara Faulkner had the "it" factor as the first woman to graduate from the Coast Guard's helicopter rescue swimmer school.
The Navy's new jacket, available exclusively to surface warfare officers, is now available for order.
The shooting was an act of self-defense, the soldier's attorney says.
The Marine amphibious assault vehicle that sank off the coast of California last week has been located in 385 feet of water.