He called Mattis "a visionary, and yet he's molded out of the same grit as Chesty Puller," citing the World War II and Korean War commander Lieutenant General Lewis Burwell Puller, whose five Navy Crosses for valor helped earn his legendary status in the Marine Corps.
Mattis offered his praise to the continued strength of the all-volunteer military.
"The summer soldiers are long gone, Mr. Secretary. And here today stands the remainder of America's awesome determination to defend herself," he said.
"After more than 10 years of war, our ranks remain filled by top quality volunteers," Mattis said, who "look beyond the political rhetoric and answered our country's call."
He welcomed Austin back to what he calls "America's varsity."