“The Wind That Shakes the Barley”IFC FilmsDirected by Ken LoachWritten by Paul LavertyStarring: Cillian Murphy, Padraic Delaney, Liam Cunningham, Orla Fitzgerald, William Ruane, Gerard Kearney and Roger AllamRated R/127 minutesOpened April 13, 2007Three out of four stars

The Cannes Film Festival has a history of awarding some of the most challenging and, often, controversial films in its competition each spring.

The winner of last year’s Palme d’Or (the festival’s highest honor) was Ken Loach’s “The Wind That Shakes the Barley,” a personal story set in the Irish War of Independence in the early 20th Century.

Like past Palme winners such as “Dancer in the Dark” and “Fahrenheit 9/11,” Loach’s film is brimming with political indignation and fervor. Many attributed the film’s Cannes triumph to its relevant social content in the face of current world affairs. “Barley” takes aim at political occupations and cultures of violence; the British soldiers foster an atmosphere of oppression and violence that virtually necessitates a similarly violent uprising.

In fact, these kinds of political parables seemed to be popular at Cannes last year — Guillermo del Toro’s “Pan’s Labyrinth” and Rachid Bouchareb’s “Days of Glory” examine similar themes, and both played in competition alongside “Barley.”

Of the three, “The Wind That Shakes the Barley” is the weakest, though it remains a potent and affecting drama despite its unevenness.

Though fictional, “Barley” draws from several real-life events and people from the Irish War of Independence. The film doesn’t limit itself to just the typical “people rising up against an oppressor” formula, but actually ends during the onset of the Irish Civil War-which stemmed from the controversial Anglo-Irish Treaty. The treaty divided the Irish people: Some saw it as a huge step forward on the way to Irish independence, while others saw it as the Irish selling out.

It is interesting to see which characters in “Barley” are on each side of the treaty debate that led to civil war. The two primary characters are brothers Teddy (Padraic Delaney) — a militant leader of a local cell of the Irish Republican Army — and Damien (Cillian Murphy), a young doctor who prefers more peaceful means until a random act of violence by British soldiers suddenly — and unconvincingly — spurs him into joining his brother in the fight.

Loach keeps the tensions at a low decibel level throughout, creating a tremendously effective, naturalistic feel to the action and dialogue. The film’s almost documentary-style narrative can be unnerving and gripping, but never sensationalized.

This very lack of cinematic embellishment contributes to the film’s complex and layered effect. Loach doesn’t paint the British/Irish conflict as an easily solvable problem, nor does he present his Irish protagonists as mere romantics or idealists.

Quite the opposite. The Irish are constantly at odds; even before the treaty causes a major division between the people, they are divided. They argue and disagree about what is right, about what compromises they can or cannot make, on how much violence is necessary before they end up behaving just like the British, etc.

Without getting too in-depth into any one character’s life, we seem to know and understand the Irish characters through their conflicts and passions.

Of course, this runs in contrast to the characterizations of the English soldiers, who are portrayed as cartoonishly ruthless — but the soldiers are not central enough to the story for that flaw to be too much of a distraction.

The problem Loach runs into is his attempt to emotionally resonate through “Barley’s” two main characters. Teddy and Damien are brothers whose lives and ideals progress over the course of the film, and the screenplay by Paul Laverty wants to establish that relationship for dramatic reasons that become apparent in the third act.

The film, however, fails to establish their relationship. There is never any concrete bond between the two characters. You can hardly tell they’re brothers. Damien could very well have been the brother of any one of the main characters and it wouldn’t have made any difference. And we know Teddy only as the leader of a local faction of the I.R.A. — not in relation to Damien or anyone else.

For these reasons, the contrived developments during the film’s final stretch don’t resonate as they are intended to. A deeper exploration of the two brothers could have served the film’s needs in that respect.

Perhaps that melodramatic focus wasn’t necessary in the first place. Material like this, examining a fascinating period in history, is potent enough as it is.

“Aye, at last a place for me sunken cheeks, right here in the heart of the Eire.” Cillian Murphy takes a stand for Irish independence in “The Wind That Shakes the Barley.”