For her to be accepted in the "man's world" of the Corps, she has had to be tougher than most to earn the respect of her peers.  Mac's Unrelenting demand for respect casuses her to take her job as a JAG officer very seriously; which sometimes places her  in a head-to-head confrontation with Rabb, telling him exactly what she thinks.  Together Rabb and MacKenzie make a formidable team and one of which the military is proud. 

Mac's mother left her with her abusive father, although he never laid hands on Sarah, when she was a child.  Sarah fought an alcohol addiction in her teen years.  After a high school friend died in a car accident that she lived through, Mac's Uncle Matt took her to Red Rock Mesa in the desert to "dry out."

Mac was commissioned through Officers Candidate School (OCS) and served with Unit 29 in Bosnia.  MacKenzie, als, bears an uncanny resmeblance to Lieutenant Diane Shonke, a young Naval officer who was murdered.  Dalton Lowne convinced early in late 1997 to leave JAG for a private law firm, but she quickly discovered that the Corps and JAG was where she wanted to be.

Major MacKenzie was stalked and abducted in early 1998, by a disturbed detective with the D.C. police.  As a result of the stalkers efforts, here former boyfriend, D.C. lawyer Dalton Lowne was murdered.  That was the only time she had regressed and gotten drunk.