In so many Civil War-era photographs, a bone-weariness of spirit lurks in the soldiers' eyes. Plenty of actors can fake that sort of thing, but Matthew McConaughey really does have it. He looks convincing in "Free State of Jones," a historical biography that is equal parts intrigue and frustration, written and directed by Gary Ross.

McConaughey plays Newton Knight, like Oskar Schindler an anomaly in a horrific time and place. Knight, a pro-Union Mississippi native, marshaled a guerrilla war against his own side, the Confederates, with troops (as many as 500) including deserters and runaway slaves alike. In modern-day Mississippi, this "Southern Yankee" remains a hugely divisive figure.

He fathered five children in his common-law marriage to a former slave and nine more with his wife. Both families shared the same 160-acre farm. Progressive hero or backwoods disgrace? Even if you carve Knight's rich personal life out of a cinematic retelling (which would be pretty stupid), you'd still have a rebel who, in 1864, managed to prevail over the Confederates in Jones County, Miss., and declare the county the Free State of Jones.

That is highly promising movie material, albeit squarely in the White Savior division of racially conscious historical biopics (i.e., the easiest to bankroll in Hollywood's eyes).

As the film begins, Knight scrambles across battlefields as a Confederate medic; soon his eyes are fully opened to the war's costs, and the way it grinds through white and black lives. Ross' script, the unwieldy result of what appears to have been a rabbit hole of historical research, deftly sets up Knight's moral awakening.

In an early scene, Knight breaks the terrifying neck shackle loose from the formerly enslaved Moses Washington (Mahershala Ali). In the Reconstruction-era sequences, "Free State of Jones" turns much of its attention to Moses and his efforts to register voters among newly freed slaves. Knight's own postwar activities are rather hastily covered, and you can tell Ross ran into some trouble working everything in.

There also are flash-forwards to 1948, where Knight's great-grandson Davis Knight is on trial for miscegenation versus the state of Mississippi. The leaps ahead are meant to illuminate how things have changed, and how they haven't, but the interpolations feel uncertain.

With extreme tact, "Free State of Jones" establishes the domestic mosaic of Knight's domestic lives. Gugu Mbatha-Raw portrays the slave-turned-common-law wife, Rachel; Keri Russell has a couple of scenes as Knight's first wife, Serena, and at one point Serena calms Rachel's newborn and the women share an "isn't this nutty?" laugh that hints at everything Ross can't make time for in a 139-minute movie. He's a filmmaker (he did well with the first "Hunger Games," among others) of considerable taste, but often in "Free State of Jones" we feel like visitors to a historical re-enactment site.

At times the movie threatens to turn its protagonist into a male version of Katniss Everdeen, glamorous, indomitable leader of the rebellion. McConaughey is too wily and skillful an actor to falsify his end of the bargain. Ross' smooth, steady film is just interesting enough to make you wish it were a lot grittier, and better.