Billionaire activist hedge fund managers have a new weapon in their corporate battle arsenal: Making movies.

First it was Bill Ackman with his 13-minute documentary on Herbalife victims.

Now hedgie-cum-director Dan Loeb has unveiled a video, “Broken Promises,” laying out his complaints about Dow Chemical.

“It’s the story of an American company … that has lost its way,” the video begins — in an effort to be more compelling than a lengthy PowerPoint presentation or just another cranky letter sent to the board of directors.

Loeb’s Third Point, one of the Dow’s largest shareholders, launched the three-minute video and a new Web site value-dow.com Thursday after talks with Dow broke down over new board members.

The video, with foreboding mood music and a baritone voice-over showing photos of Dow’s offices and execs, says Dow “continues to break its promises to shareholders” because as the video says, Dow hasn’t met its earnings projections in recent quarters and cut its dividend, which it promised not to do.