The Marines of Darkhorse Battalion suffered a high rate of casualties during their seven-month deployment to southern Afghanistan. Their mission was to go after the Taliban in a place called Sangin — a crossroads of insurgency and drug trafficking. At the time, officials in the military and all the way up to the secretary of defense asked why the Darkhorse Battalion was taking so many casualties. NPR Pentagon correspondent Tom Bowman is reporting all week on the battalion. On Wednesday, he speaks with Guy Raz about the strategy in Sangin: whether the Marines made mistakes and what they did to reduce causalities and complete the mission.