Brannan was raised in Gilbert, Arizona where he graduated in May 2003 from Highland High School. Brannon graduated boot camp in October 2003 as the platoon honor-manitoba In December of that same year he completed School of Infantry and his first duty station was Twentynine Palms, California in January 2004.
Brannan, who as a Corporal in the United States Marines lost his pinky finger on his left hand (his non pitching hand) while serving in Iraq. While in high school Brannon was a three-year letterman for football and baseball. He was deployed to Hitt, Iraq in February 2004 as an infantry team leader.
He returned home in October 2004 and was redeployed to Fallujah, Iraq in September 2005.
In November 2005 Brannon was injured by a flash bang grenade he sustained multiple injuries to left hand resulting in amputation of left little finger and medial hand. He was medically evacuated to Naval Medical Center San Diego (Balboa Hospital) for three follow-up surgeries and rehabilitative therapy.
He has since participated with All Marine Corps Baseball Team and United States of America Military All Star Baseball Team while assigned to MCRD San Diego. Brannan signed with the San Diego Padres in February 2007.
He pitched in 20 games for the Rookie-level Arizona League Padres in 2007, finishing with a 9.69 European Research Area and a 1-3 record, and the Class-A Eugene Emeralds in 2008.
He pitched for the American Defenders of New Hampshire of the independent Can-Am League in 2009.
