BEVERLY HILLS, Calif. (AP) — When it comes to canine stars, like their human counterparts, sometimes it's all about the look.

Before he'd even conceived of what would eventually become "Max," director Boaz Yakin knew what he didn't want: Something cute.

"It'd been a long time since anyone made a movie where the dog was just treated as a hero, as the protagonist, without any cuteness or cloying the way Rin Tin Tin was back in the 20s, or the way Old Yeller was in the 50s," said Yakin.

His friend and eventual co-writer Sheldon Lettich, a Marine and Vietnam veteran, suggested basing it around a military working dog (MWD), and the narrative started to take shape.

Casting the eponymous hero of "Max," the story of a PTSD-afflicted military dog that moves in with his deceased handler's family, in theaters Friday, was its own beast. Yakin decided the breed should be Belgian Malinois, a staple in the military and law enforcement agencies in the United States. But he wasn't looking for just any Belgian Malinois; he needed a one-in-a-million pup.

The breed typically sport a black snout that extends to the eyes like a mask. Yet that was going to present a major problem on camera.

"It's very hard to read their eyes on film," said Yakin, who knew that expressive, distinctive eyes were going to be essential for telling the emotional story about Max's return from Afghanistan.

So Yakin challenged the Hollywood critter company Birds and Animals Unlimited (whose credits include "Marley and Me," ''The Shaggy Dog" and "Hotel for Dogs") to find a Belgian Malinois with lighter fur on its face.

After an extensive worldwide search, they found exactly what they were looking for in Kentucky: A spirited, untrained 2-year-old Belgian Malinois named Carlos.

"He's got the most beautiful face and he's really smart," said Mathilde DeCagny, a trainer on the film.

DeCagny worked with Carlos five days a week for three months to prepare him for his role, which would require the dog to squirm, fight, bite, and emote on command.

But following in the tradition of all great movie mutts, Carlos wasn't the only Max in "Max."

"We didn't want to use him for stunts and things where he could potentially get injured and tired," explained DeCagny.

In total, there were five Belgian Malinois on set, all of whom had to get their faces professionally dyed to match Carlos's unique look.

If Carlos is the star, Jagger is the pinch-hitting understudy. Decidedly mellower than the "eccentric" lead, Jagger was called to bat when the scene required more emotion. Still, Yakin said, when Max has a close-up, it's probably Carlos.

The others were more stunt doubles, used for wide shots and the action sequences — which were staged with the utmost care. In order to show two Rottweilers running after Max, for instance, the production filmed each dog running separately and edited the footage together to look like a suspenseful chase.

Ultimately, "Max" earned the highest possible grade for animal safety from the American Humane Association.

"I was shocked at how well-trained they were," said star Josh Wiggins. "It was very specific stuff that they told him to do. They could tell him to kiss, and lick and put their tongue back in their mouth. It was crazy."

While Yakin didn't have to do much directing of the pups, since everything was coordinated with the trainers in pre-production, the bulk of the responsibility was on the actors. They had to stay composed and focused even when the trainers were behind the camera shouting commands.

For Wiggins, whose character helps Max re-enter the world, it wasn't much of a stretch to spend his days with a pack of pups. Not only do Wiggins and his family have three (a Rottweiler, a Labrador Retriever and a Chiweenie), his father actually trains bomb-sniffing dogs for the Houston Police Department.

Wiggins, who also has a brother in the military, is excited by the prospect of people learning a little more about military dogs.

"A lot of people don't recognize what bomb dogs really do," he said. "A lot of times they go through the same emotional trauma as people."

___

Follow AP Film Writer Lindsey Bahr on Twitter: www.twitter.com/ldbahr