Sitting with his head in his hands, dressed head-to-toe in military camouflage, in the opening sequence, the 41-year-old actor’s latest role as Special Forces Sergeant James Harper is as physical as they come.

And that opening will undoubtedly tug at the heartstrings – The Contractor is as much about emotion and family bonds, as it is about action, respect and reflecting on the treatment of former military personnel.

“It’s a great ride. It’s a great thrill. It’s a great action piece,” says Pine with a nod.

“But at the heart of it, it’s a character study of a man who’s stripped of everything that he holds dear. Everything that he’s built his life around – freedom, honour, democracy, protecting values, his whole life has been taken away from him.”

A career that started with a string of rom-coms including This Means War, The Princess Diaries 2 and the Lindsay Lohan-led Just My Luck, Los Angeles-born Pine initially found himself typecast as the young Hollywood heartthrob.

Now though, the tables have turned. A name more likely to be associated with deep space courtesy of his role as Captain James T Kirk in JJ Abrams’ hit Star Trek films, a string of subsequent action roles including Hell Or High Water and The Finest Hours have cemented Pine as something of a go-to action lead.

Written by JP Davis (The Plane) and directed by Westworld and Ray Donovan director Tarik Saleh, The Contractor sees Pine’s character – a former Green Beret – attempting to re-adjust to the outside world following an honourable discharge from the military.

As the former sergeant finds himself without a pension, increasingly in debt and with a family to support, he takes a job as a military contractor in Berlin. It’s a position which sees him hunted by the very camouflage-clad personnel that once employed him.

Described as a “deceptive” story by Pine – primarily due to its strong moral and emotional frame, hidden beneath the classic hallmarks of a thriller – the project is one the US actor describes as a “very 21st century view of warfare”.

“[The Contractor] has nothing of the black and white, morally monochrome, World War II vision of the world, of good versus evil,” adds Pine.

Joined by fellow Hell or High Water and Finest Hours star Ben Foster as brother-in-arms Mike Denton, the pair’s on-screen relationship needed to be a close, brotherly bond – as is so often the case with military personnel.

To ensure authenticity remained paramount, the film’s language, movements and action sequences were all meticulously dissected, guided by former soldier-turned-military consultant Bert Kuntz. The ex-US Army Special Forces Green Beret originally worked within a specialist unit known as Cif – the commanders in extremis force, known for its hostage rescues and high stakes missions.

“The biggest nightmare with what we do – and it’s not such a huge nightmare as it is just soul crushing, is that somebody in a green beret is like, ‘Nah, I wouldn’t move like that’,” says Foster, 41.

“The Army has a different procedure of entering a space than the Navy does. And finding those unique signatures in an accelerated learning process, drawing upon previous training, you start building a physical ability – you hope.”

Describing how the actors “couldn’t let [military personnel] down”, Foster says both he and Pine felt the weight of responsibility when it came to representing the armed forces on screen. Noting the difficulty that comes with “walking a line of genre without sacrificing character”, Foster says difficult choices had to be made in terms of content, which led him to become “more interested in the questions, than I suppose the answers”.

“You feel a responsibility to the community because these are people that are using these techniques in life or death situations,” agrees Pine, staring down the camera during our video link call. It’s a burden the actor in fact clearly relishes, given the way in which he freely admits to “nerding out” on all things military-related.

“I remember when I was a kid, my mom gave me a Barbie doll and I ripped off its head and I turned it into a gun,” smiles Pine, reminiscing. “So it’s like, there’s some little… I love all that technical stuff, using the [equipment] and how you load it – because it’s all pretend for me, I don’t actually have to go to battle.”

Action sequences aside, The Contractor, which arrives on Prime this week, also highlights a wider conversation. Given the sheer number of former military personnel suffering from PTSD and other warzone-related physical and mental health issues, should more be done to assist those in need after their duty to their country has come to an end?

“It’s a huge, huge issue,” says Pine, suddenly taking on a more sombre tone. “It’s something we talked a lot about while we were filming. Ben, correct me if I’m wrong, but I think more soldiers die from self-inflicted gunshot wounds than they do in a [hospital] theatre, is that right?”

His co-star nods in agreement, citing a 2012 Veterans Health Administration Suicide Data Report which suggests that between 18 and 22 veterans die from suicide every day.

“I mean, there you go,” Pine says. “It’s very important to talk about and I’m glad we raised it in our film – we could have spent more time on it, but at least, maybe, it’ll make people think and ask some questions.”