[2] He graduated from the University of Idaho in 1970 with a Bachelor of Science degree in finance and economics, and was commissioned as an ensign in the United States Navy through Naval Reserve Officers Training Corps on January 23, 1970.

Joining Marine Fighter Attack Squadron 212 (VMFA-212) in the spring of 1972, Amos's ensuing operational assignments included tours with VMFA-235, VMFA-232, and VMFA-122, where he flew the F-4 Phantom II.

[4] After a three-year posting as a flight instructor in advanced jet training, attendance at the Armed Forces Staff College in Norfolk, Virginia, as a major, and a 13-month overseas staff assignment to the III Marine Amphibious Force, Okinawa, Japan, Amos was transferred to Marine Aircraft Group 24, Kaneohe Bay, Hawaii.

Following a two-year staff instructor assignment at Quantico, Virginia, where he was promoted to colonel, Amos took command of Marine Aircraft Group 31, Beaufort, South Carolina in May 1996.

Promoted to brigadier general in 1998, Amos was assigned to NATO as the deputy commander, Naval Striking Forces, Southern Europe in Naples, Italy.

Receiving his fourth star in July 2008, Amos assumed duties as the 31st Assistant Commandant of the Marine Corps, based at the Pentagon in Arlington, Virginia.

[11][12] Additionally, during his final two years as commandant, he shepherded the corps' considerable efforts to address head-on its many challenges in recruiting and maintaining a diverse and talented body of marines.

[15][16][17] After a decade plus of declining amphibious ship numbers in the U.S. Navy inventory, and increasing operational requirements for marines around the world, Amos partnered with the Chief of Naval Operations, the Navy Secretariat, and industry to reconfirm amphibious ship requirements, acceptable readiness levels, and total hull numbers.

This single agreement alone will result in millions of dollars saved over the lifetime of the LSD replacement effort, and will accelerate the completion and delivery of the ships years ahead of schedule.

[18] In 2012, Amos partnered with key legislators In the US House and US Senate to bring national recognition to the service and sacrifices of the corps' African American Montford Point Marines with the awarding of the Congressional Gold Medal.

Their unique service to the United States had never been recognized at the national level until Amos initiated efforts to have them awarded the Congressional Gold Medal.

[23] After President Obama signed the legislation setting the conditions for repeal, Amos led the Department of Defense in carrying out the will of the nation's civilian leadership.

[24] In late November 2011, Amos stated that his opposition to gays openly serving in the military has proven unfounded and said that Marines have embraced the change, describing the repeal as a "non-event.