After premiering on the festival circuit last year, the latest documentary from acclaimed director Errol Morris will be getting a limited theatrical and VOD release this April. The Unknown Known is somewhat similar to his 2003 Academy Award-winning film The Fog of War in that it is another portrait of a former U.S. secretary of defense. This time around, however, he is not able to extract as many nuggets of wisdom from Donald Rumsfeld as he did from Robert McNamara. Some have criticized Errol Morris for being unable to pin down Rumsfeld and allowing him to evade many of his questions, while others have argued that this is precisely what makes the film so fascinating. The Unknown Known hits theatres on Apr. 4th; check out the trailer after the jump and see what you think.