Armies have been using dogs in battle for thousands of years. The Romans would turn the dogs on their enemy as a signal of the approaching legions, hence the expression “let loose the dogs of war”. But in recent decades dogs have found a new, perhaps more noble calling during wartime. Dogs have been used to search for lost soldiers. They have been trained to assist wounded soldiers. They have also learned to sniff out explosives, helping to clear mines and saving the lives of their handlers and hundreds of soldiers and civilians. That's the kind of dog Rex is. And you'll fall in love with him just as the titular character Megan Leavey did. The movie Megan Leavey is a bit of a character study, and one of those characters is a German Shepherd.

Kate Mara stars as Megan Leavey. Her life has been pretty much a screwup, and she's facing pressure to get it together. She decides to join the Marines. At first it appears she's going to fail at this choice, too. But slowly she begins to get her training on track and starts to make the grade. Her inspiration? She is attracted to the canine unit, where she is first sent for punishment, but discovers Rex. Rex is a dog the vets don't think is trainable. He's aggressive, and very much like Megan, has a mind of his own. So Megan puts in the extra effort in the hope she can join the unit and work with Rex. Of course, she ends up getting her wish, and the two are sent to Iraq, where they are able to save lives by finding mines so they can be disarmed. It's a dangerous job, and their number ultimately comes up. It seems the enemy targets these dogs to protect the minefields. Wounded, the pair return home where the true battle is fought. The vet has labeled Rex unadoptable, and Megan fights to allow him to retire with her.