Ralph Fiennes turns one of Shakespeare's least-loved plays into a slashing, muscular but uneven modern drama in his film-directing debut. "Coriolanus" opens powerfully with scenes of rioting citizens in bread lines that could have been taken from live TV coverage of Eurozone economic protests, moves through viscerally exciting run-and-gun battle scenes and for long stretches delivers its characters' poetic dialogue with rare emotional clarity and power. The longer it runs, alas, the murkier it becomes.

Fiennes plays the title role, a battle-scarred (and often blood-smeared) Roman general whose bravery is second to none but whose attitudes are proto-Fascist. Coriolanus falls from grace when he's advised to suck up to the public in order to run for political office. Scorned by the ungrateful rabble when he is unable to conceal his contempt for them, he defects to the enemy Volscians and prepares to unleash hell on his fickle countrymen. And that only takes us up to Act III.

The screenplay by John Logan ("Gladiator") streamlines the play with press conferences, news reports and a chorus of TV talking heads but can't clarify the antihero's bipolar sulks and rages. There's something much deeper here than post-traumatic stress or a career soldier's inability to adjust to civilian life, but what?

With his fearsome glower dialed up to 11, Fiennes makes a searing impression, but the character's unpredictable, continually shifting allegiances make Coriolanus one tough dude to understand. At various times he is for or against Rome, the Volscians, his trusted political adviser (Brian Cox), his mortal enemy Aufidius (Gerard Butler) and his own mother (Vanessa Redgrave).

Fiennes has an unexpectedly strong visual sense, framing his scenes for maximum tension and cutting with staccato speed. The film was shot around Belgrade by Barry Ackroyd who also worked on "The Hurt Locker" and brings that film's bruising authenticity to bear. It comes as no shock that Fiennes is a superb director of actors, with a rare gift for unpacking the nuances of Elizabethan speech. When the sense of what he's saying is sketchy, his glacier-blue eyes tell everything.

Redgrave is a ramrod as his domineering mother Volumnia, herself a high military officer with a carnivorous appetite for family glory. "Had I a dozen sons," she says, "I had rather eleven die nobly for their country than one voluptuously surfeit out of action." As his faithful adviser Menenius, Cox is an utterly convincing politico. They'd recognize his character immediately on K Street.

Given Logan's freewheeling cuts (he lopped half the text) and inventions, Shakespeare fans may have more difficulty recognizing the play, and the passions firing the proud warrior's suicidal battle with himself.