The pair served two deployments in Iraq together, first to Fallujah in May 2005, and then to Ramadi in May 2006, where she and the German Shepherd were both wounded the following September by an improvised explosive device (IED) while she and her dog were leading a U.S. Army patrol down a street.

[3] Leavey first sought to adopt Rex before she was honorably discharged from the Marine Corps in December 2007 with the rank of corporal.

[4][1] Four years later, when Rex developed facial palsy that ended his bomb-sniffing duties, Leavey again petitioned the Marine Corps for his adoption.

[4][5] In April 2012, "Sergeant Rex" was retired by the Marine Corps at Camp Pendleton's K-9 unit and Leavey and the dog were reunited through the intervention and support of Senator Chuck Schumer, Randy Levine and his wife Mindy, president of the New York Yankees baseball club, and others.

[8] Leavey is portrayed by Kate Mara, and had a cameo appearance in the film as "Female Drill Instructor #3".