TORONTO — It's regarded as one of the most expensive Canadian films to hit the big screen and boasts a grand vision that its writer, director and star Paul Gross began formulating in his mid-teens.

In terms of epic tales, "Passchendaele" meets the definition on several levels, not the least of which is the ambitious recreation of the horrific First World War battle, in which 16,000 Canadian soldiers sacrificed their lives to capture a German stronghold that eluded other Allied attacks.

For Gross, this piece of Canadian history is a remarkable feat he felt compelled to honour with a cinematic tribute to military valour and personal sacrifice.

"In general, I think we're losing that history of the First War and I think it's a sad thing," Gross said earlier this year when the film opened the Toronto International Film Festival.

"I hope that in some small way the film can rekindle some interest in it because in my mind that's where we really were forged as a country, somewhere in those battlefields of western Europe. The war was such an enormous hinge in history -- it wiped out five empires, gave birth to two new ones, just utterly booted religious orthodoxy, eliminated monarchy, at least in the western powers, changed art, science, medicine, everything was completely changed as a consequence of it.

"And Canada stepped out from under the shadow of Great Britain and stood on its own two feet, really, I think for the first time as an independent country. A lot of how we came to think of ourselves was formed there."

Gross's interest in the Great War began with tales from his battle-scarred grandfather, a man tormented by the horrors of Vimy and the brutality that he discovered in himself in the midst of combat.

One of those stories comprises the opening scene of "Passchendaele," in which the film's hero, Sgt. Michael Dunne, played by Gross, ruthlessly slays a young German soldier at close range. Gross says his grandfather remorsefully confessed the killing to him when he was a teen and it was a senseless act of violence that haunted the veteran to his deathbed. Gross says the shocking tale lingered with him, too, as he struggled to comprehend the heinous extremes of humanity.

"There are those events in our lives where a door kind of swings open on something else and for me it was on a life of adulthood, I guess, and on a life of consequence," he says of the impact of that war tale.

"Ever since then I've been interested in trying to do something with it."

Gross began writing "Passchendaele" some 12 years ago, and soon realized that the sprawling epic he envisioned would require an extensive cast and a massive budget. For a while, he says he considered making the film as a co-production with either the United Kingdom or Germany, but that would have required compromises to the script that he was unwilling to make.

"We really wanted it to be a Canadian story," explains Gross, whose directorial debut came 2002 with the romantic comedy "Men With Brooms."

"The only way it would have worked say, with the U.K., would be to make the main character a Brit who has just arrived in Canada."

He stuck to his guns for years. In the end, funding came from a blend of public and private sources, with the Alberta government providing $5.5 million from a centennial legacy fund.

"Passchendaele" was filmed and largely set in Alberta, with the epic battle shot at an aboriginal reserve just outside Calgary. This was a feat in itself, since the engagement was marked by a punishing rain that turned the Belgian landscape into a thick muddy swamp by the time the Canadian Corps launched their attack in October 1917. Gross says he had to truck in thousands of tanks of water from the frigid Elbow River and the resulting muck often immobilized cast, crew and equipment.

But visually, it provided for a mesmerizing vista, he says.

"The landscape is so blasted, it always just struck me that this was the ideal battle to use, cinematically, because it was like the moon, but wet," says Gross, who balances the brutal battle scenes with a tender love story featuring Montreal actress Caroline Dhavernas ("Hollywoodland," "Wonderfalls").

"It was without question the worst condition I've ever shot in," he continues.

"Whenever we stood in that battlefield and the mortars were going and the machine guns were firing you did get the sense that `Oh my God, this is what it was like.' It didn't take a lot of imagination to put yourself there. And I have no idea what breed of man they were, I don't know how they did it, I know I wouldn't last for a minute."

"Passchendaele" opens Friday across Canada. The filmmakers have not secured distribution elsewhere, but Gross has said such deals would be necessary to recoup the film's massive cost.