As questions continue to mount about the Niger firefight that killed four U.S. soldiers in early October, here's a timeline on what happened based on new details from the Department of Defense. U.S. military officials sought permission to send an armed drone near a patrol of Green Berets before a deadly ambush Oct. 4 in Niger, but the request was blocked, raising questions about whether those forces had adequate protection against the dangers of their mission. New information shows the Green Beret team was part of a larger mission, one potentially more dangerous than initially described, and one believed to merit an armed drone. But the request was blocked in a chain of approval that snakes through the Pentagon, State Department and the Nigerien government, according to officials briefed on the events. One focus of military investigations into what happened in Niger will be what a military official now says were two changes in the mission of the Green Beret team--from initially training Nigerien forces, to advising on a mission to capture or kill a wanted terrorist, to investigating the terrorist's abandoned camp.