Gerard Butler is showcased in a new trailer for “Machine Gun Preacher.” His character finds a purpose in life after he tangles with a Sudanese warlord in an effort to prevent him from enlisting children in his army.

The plot sounds so Ramboesque it’s hard to believe, except its based on a true story.

Butler plays Sam Childers, a real-life biker and ex-drug addict, who builds an orphanage for wounded kids and child soldiers in the Sudan.

But first he has to take on the Lord’s Resistance Army. Childers finds God, which launches him on his crusade for justice.

Ultimately, Childers is forced to organize his own militia to protect the children. In a sense, he sinks to the warlord’s level, but does the end justify the means?

Marc Forster (“Monster’s Ball, “Kite Runner”) directs the picture which also stars Michelle Monaghan and Michael Shannon.

The real Sam Childers grew up in the hills of Pennsylvania. His parents were decent, honest people but at an early age Sam was trouble.

His father, a former marine, grew fond of saying “Boy, somebody’s gonna kill you one of these days!” according to his official bio.

After an early life of hard drugs and hard times, Sam founded a successful construction company and was urged by his Pastor to join a mission group to help repair huts damaged in Sudanese conflict.

That’s when his life took a dramatic turn.

The film that will be released Sept. 23.