(CNN) -- The assault began at dawn, as bullets and rockets peppered the remote outpost in eastern Afghanistan.
Lt. Cason Shrode said that in less than two minutes, his team's generator was hit and they were out of power.
The insurgency was so fierce, according to one soldier, that the troops couldn't get to their mortars to fire back.
"They were under heavy enemy contact," Sgt. Jayson Souter said, describing the October 3 attack that pinned his comrades at Combat Outpost Keating, a remote base in Nuristan province.
Four servicemen -- Souter, a fellow soldier, an Apache helicopter pilot, and a gunner -- talked to a military reporter about their roles during the Keating attack in an interview posted by the Department of Defense on Facebook and NATO's International Security Assistance Force YouTube Channel.
The United States says about 200 insurgents -- mostly local fighters, with some Taliban organizers and leaders -- had been planning the attack for days, hiding mortars, rockets and heavy machine guns in the mountains. Watch more about their story »
The battle started early on October 3 and lasted for 12 hours. At the end, eight American soldiers and more than 100 militants were killed and buildings at the outpost were destroyed.
Fire support officer 1st Lt. Cason Shrode said the initial round "didn't seem like anything out of the ordinary." There was a lull and then there was a heavy attack.
"We started receiving a heavy volley of fire. Probably 90 seconds into the fight they ended up hitting one of our generators so we lost all power," Shrode said in the interview posted online by the Defense Department. "At that point I knew that this was something bigger than normal."
Troops called in air support. Helicopter gunner Chad Bardwell said he had to confirm the fighters he saw on ridgelines were the enemy because he had never seen such a large group of insurgents.
"We tried to stop them as they were coming down the hill. ... We were taking fire pretty much the entire day," he said in the Defense Department interview.
Chief Warrant Officer Ross Lewallen, the Apache pilot, said a few aircraft were damaged in what was a "time-consuming endeavor" governed by tough terrain. He said the morning battle was "significant," but later troops were able to identify targets and eliminate larger weapons.
"One of the primary reasons for the fight taking so long is that it is an extreme terrain," he said in the same interview.
Lewallen said the valley sits beneath mountains to the west and north.
"There's a lot of cover so you really can't detect the enemy until they start moving again," he said, adding that it was tough for medical evacuation aircraft to land "because we were still trying to control" the outpost.
The intense assault on Keating led to fires. There were five main buildings at the post and four of them burned. Soldiers eventually ended up going into one building.
"The next morning it was pretty much ash besides that one building. I mean that's the way to describe it. Most of it had burned down. So we were pretty much at one building and the rest was just a shadow of what it used to be," Shrode said in the Defense Department interview.
Lewallen said what came together was "air-ground integration."
"All the training we've done before deploying here; it really clicked that day," he said in the interview. "We started realizing that the guys on the ground knew what they needed to tell us to get the job done. It made things that much easier."
He disputed media reports suggesting that there weren't enough weapons and troops. He said 40 minutes into the fight, air power arrived.
"We had everything we needed. It was just a big attack with a lot of people. Bad things happen -- but I think we did well, under the circumstances."
Reflecting on the fight, Souter said, "Everybody basically came together and in the mix of it all, they were donating blood for the wounded that we had. They all pulled together to make sure that we can pull our boys out of this."