On the night of her graduation, she was traveling in a car with her friend Eddie. They were both drunk, and were involved in a car accident that killed Eddie. Her uncle USMC Colonel Matthew O'Hara took her to Red Rock Mesa, Arizona, to dry out. Mac later repaid the debt owed to him by making sure he did not get killed during an incident where he and a group of rogue Marines hijacked a van transporting the Declaration of Independence. After graduating from high school and then at some point earning a bachelor's degree, Sarah MacKenzie joined the Marine Corps and received her commission through Officer Candidate School. The first known assignment for Mac in the canon was at the grade of first lieutenant at the Headquarters and Service Battalion in Okinawa, Japan, as an administrative officer under John Farrow. It was under his recommendation that Mac was sponsored by the Marine Corps to earn a law degree at Duke University School of Law. While stationed in Okinawa, Mac engaged in an affair with her superior officer John Farrow. Unbeknownst to Mac, Christopher Ragle followed her to Okinawa and discovered the affair. She was stationed in Bosnia and Herzegovina a year before the events in at the start of the second season, at some point with 2nd Battalion, 9th Marines ("Two Nine") for unknown duration, and given the time-line, was likely part of or associated with the Implementation Force (IFOR), following the 1995 Dayton Agreement. As a major, she was subsequently assigned to JAG headquarters in Falls Church, Virginia when she was pulled off a double homicide investigation to work on a case involving her uncle Colonel Matthew O'Hara (Carmen Argenziano) who had the stolen Declaration of Independence. Lured by her then-boyfriend Dalton Lowne (Larry Poindexter) and the glamour of private legal practice, she resigned her commission to work as an attorney at the White-shoe law firm "Lowell, Hanson and Lowne". However, soon changing her mind after successfully defending Harm pro bono in a court martial, she asked Rear Admiral A.J. Chegwidden (John M. Jackson), Judge Advocate General of the Navy to take her back at JAG. Chegwidden gave her back her letter of resignation, claiming he had been "too busy to process it" (despite having had at least four weeks in which to do so). When Christopher Ragle (Joe Lando) caught up to Mac at JAG headquarters in