Review | Napoleon who? Ridley Scott biopic leaves a void at its center.

Such are the contradictions of a movie that soars with ambition and historical sweep, even as it fails on some basic fundamentals. Working from a script by David Scarpa, Scott brings his most impressive technical skills to bear on a story that’s uniquely well-suited to extravagance and overstatement. As the film opens, Marie Antoinette is being beheaded during the French Revolution, a rite that Scott stages with graphically gruesome detail. During the ensuing Reign of Terror, we meet Napoleon Bonaparte, a Corsican gunner and artillery commander ordered to recapture the port of Toulon, which has been occupied by the British.

That battle would send Bonaparte on a dizzying journey up — and down and up and down — the greasy pole of French politics and military promotions, and it’s staged by Scott with sanguinary detail: Blood will spurt, spray and splatter throughout the battles that made him and undid him. Meanwhile, Bonaparte makes the acquaintance of an attractive older widow named Josephine (Vanessa Kirby), by way of her young son. Thus does “Napoleon” find its rhythm, revisiting such pulverizing chapters as Austerlitz, Borodino and the invasion of Russia while toggling back and forth to a sexual relationship that can most charitably be described as complicated.

Once its now-this, now-that structure is established, “Napoleon” settles into monotony: Those pivotal battles are executed with pomp, pageantry and faultless attention to strategic detail and human loss. The spectacles, however, lose impact as they pile up. Once the Duke of Wellington shows up at Waterloo, the fact that he’s played with such supercilious glee by the perpetually sneering Rupert Everett comes as a welcome relief. The relationship story is similarly one-note. Kirby casts a mesmerizing erotic spell as Josephine, who visibly recoils when Napoleon touches her and somehow always finds a mirror to gaze into as they make love. This is one sick twist of a tryst, with the two forming a strange — and ultimately tiresome — double helix of sadomasochistic desire and overweening ego.

Even at its most rote when cataloguing Bonaparte’s victories and setbacks, and even at its most voyeuristic when it comes to his sex life with Josephine, “Napoleon” is handsome to behold. Dariusz Wolski films the proceedings with admirable depth and clarity, and the costumes (by Janty Yates and David Crossman) are dazzling. The biggest flaw in “Napoleon,” it turns out, is the actor who plays him. It’s difficult to understand why Scott would cast Joaquin Phoenix — one of the most subtle, recessive, almost fey actors working today — to play someone with such a commanding temperament.

More than once in “Napoleon,” Bonaparte is called the greatest leader in the world, but we never really see that leadership, other than him plugging his ears and giving orders to fire. By the end of the film, we might feel as if we’ve seen him in action, but we have no better understanding of what drove him, or what he was really like. (Some questionable acting choices don’t help: At a recent screening, the audience cracked up when Bonaparte pouted to an opponent, “You think you’re so great ’cause you have boats!”) “Napoleon” is less about ruthlessness, brilliance and hubris than about a man to whom many things happened. As played by a stiff and expressionless Phoenix, he’s less a legendary leader than a passive, often petulant cipher. We don’t need another hero, but when it comes to the man at its center, “Napoleon” could have used a lot more oomph.

R. At area theaters. Contains strong violence, some grisly images, sexuality and brief strong language. 157 minutes.