“Rules of Engagement” (PBS, 9 p.m.) examines the November, 2005 incident in Haditha that killed a Marine and 15 Iraqi civilians and has been called a massacre. First explained away as “insurgents” killed by an IED, further investigation revealed that the Iraqis died at the hands of U.S. forces, many in their homes. Eight Marines initially faced various criminal charges, but only four remain charged by military courts-martial, though none are facing murder charges. With the criminal trial of Staff Sgt. Frank D. Wuterich, who testified he told his team to “shoot first and ask questions later,” set to begin in early March, Marine commanders told Frontline the incident — to this day a sore point in U.S.-Iraqi relations — caused them to re-examine training and tactics. Frontline embedded journalists with Kilo Company, whose Marines were involved in the Haditha incident, giving the viewer a rare front row seat at the Roshomon of Iraq.