By Lindsey Bahr,AP Film Writer

Here's a general rule of thumb: If you're going to rely heavily on voiceover to tell your movie's story, and exclusively so in the first 15 minutes with an assault of colorful character introductions, you'd do well to make sure that the narrator is a compelling one. Unfortunately for writer and director David Michod's military satire "War Machine ," Scoot McNairy is not that narrator. A fine actor, yes, but one whose disconnected voice is at best unremarkable and at worst like Tobey Maguire on sedatives.

Alas, it is McNairy's sleepy, lengthy exposition which kicks off, and drives, "War Machine," a smart and genuinely interesting but overstuffed critique of modern warfare and the men in charge that also inelegantly whiplashes between absurdism and sincerity. And, yet, while it might not reach the heights of classic war satires like "Catch-22," or "M-A-S-H," a strong and sobering third act makes "War Machine" a worthy and thought-provoking endeavor. If only the first part held up to the finish.

At the center is Brad Pitt's General Glen McMahon, a four-star general tasked with heading up military operations in Afghanistan. McMahon is in all but name a caricature of Gen. Stanley McChrystal, the once commander of all U.S. and NATO forces in Afghanistan, who was famously destroyed by an inflammatory Rolling Stone article by the late writer Michael Hastings. The article painted McChrystal's team of counterinsurgency evangelists as arrogant and anti-authoritarian and featured derogatory comments about the Obama administration from his staff.

Michod attempts to infuse that sort of rebel energy and vigor into "War Machine" with varying results, focusing heavily on McMahon's robotic drive, delusional megalomania and his miscreant hangers on (including Emory Cohen, Topher Grace, RJ Cyler, John Magaro and Anthony Michael Hall).

Lean and sporting a blinding white-blonde military crop, Pitt uses everything in his arsenal to fully embody this man whose entire existence is given worth through war. His exaggerated facial tics, aloof overbite and perpetually clawed hands can come across at times a little actor-y, but effortlessness is not what he appears to be going for. This is not an everyman, or someone just doing a job. He is his job. He's driven by what others tell him he can't do, whether it's securing more troops or occupying an unwinnable area, and seeing his stubborn arrogance up against the bureaucratic profiteers is really something to behold.

Michod adapted "War Machine" from Hastings' 2012 book "The Operators: The Wild & Terrifying Inside Story of America's War in Afghanistan." McNairy plays the Hastings stand-in – a rumpled Rolling Stone reporter named Sean Cullen who we don't actually meet in the flesh until about halfway through. He'll bear witness to the antics of McMahon's staff, and destroy them on the page. But seeing the bravado and bluster and stupidity of these men is by far the least interesting thing about "War Machine." Except for McMahon, they're presented as fools and caricatures from the start and we never expect anything else from them.

Where "War Machine" really finds its stride, however, is in the human margins outside of the reporter's purview – especially in scenes involving the young soldiers on the ground who are haunted and conflicted by the confusing and unspecific directives given to them to execute this confusing and unspecific war. Will Poulter and Lakeith Stanfield both steal the show as some of the Marines tasked with trying to win the unwinnable area for McMahon.

In the past, Michod has excelled in stripped down milieus, like in the slow-burning "The Rover," and he does not disappoint in executing the final tragic mission, laced with heart-pounding dread and soul-aching futility. But it's a bit of a slog to get to the powerful conclusion, which is more nuanced, fair and bleak than the over-the-top first two acts might have suggested. This might not be the classic modern military satire that we needed, but it is a start – and an unflinching one at that.

"War Machine," a Netflix Originals release, is rated TV-MA. Running time: 122 minutes. Two and a half stars out of four.

MySHOOT Profiles