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.

The ambush in Niger earlier this month that left four U.S. troops dead has been the subject of immense speculation, not only concerning President Trump's public response to the tragedy but also about what actually happened on the ground that day. Asked by Fox News on Capitol Hill if the administration has been forthcoming about the attack, Armed Services Committee Chairman Sen. John McCain, R-Ariz., replied, "of course not" and added, "it may require a subpoena." Defense Secretary Jim Mattis said Thursday that the attack is under investigation. A dozen U.S. Army soldiers, mostly Green Berets, along with 30 Nigerians, traveled 125 miles north of Niger's capital, Niamey, in unarmored trucks on a routine mission and to meet with local village elders in Tonga Tonga, near the border with Mali, on Oct. 4. U.S. Army Sergeant La David Johnson was killed when his patrol was ambushed in Niger.

After an intense two-day search, local military forces Friday recovered the body of a U.S. Army commando who was inadvertently left behind after a daylight ambush by militants killed three other Green Berets in a rugged border region in Niger. Pentagon officials had not previously announced that a Green Beret was missing in action after the surprise attack on a joint patrol of U.S. commandos and Nigerien troops Wednesday. Six of the 12 Americans on the patrol were killed or wounded. Officials hoped the missing U.S. Army Special Forces operative might still be hiding in the dense brush, rather than taken captive, and launched a massive search-and-rescue mission with aerial drones and other aircraft, as well as Nigerien ground forces. The death of four Green Berets in remote West Africa marks the worst single loss of U.S. forces under fire since President Trump took office.

Two other Special Forces soldiers were also wounded in the Niger ambush; Lucas Tomlinson has the story for'Special Report.' There was no U.S. surveillance drone overhead at the time of the ambush in Niger which killed three U.S. Army Green Berets and wounded two others Wednesday, multiple officials familiar with the matter tell Fox News. In addition, Fox News has learned the dead and injured soldiers were taken from the firefight by French Puma helicopters. Only one U.S. helicopter was available to pick up the Green Berets. It is not clear why it wasn't used.