Staff Sgt. Clint Romesha was taking stock: His small outpost nestled in a remote valley of a mountain range in eastern Afghanistan was under attack by hundreds of insurgents.

Three American soldiers were dead, killed by militant snipers hidden in heavy brush on the side of the mountains.

Three were trapped in a mortar pit. Five more -- two of his close friends included -- lay pinned down in a Humvee, taking heavy fire. Others were badly wounded.

Romesha, who had a hole in his arm from a rocket-propelled grenade, was trying to figure out who was alive and who was dead.

Then a call went out on the radio: ENEMY IN THE WIRE.

The insurgents were now inside the camp.

Story of valor

The battle for Combat Outpost Keating -- considered one of the worst ground attacks during the Afghanistan war -- is a cautionary tale.

It's the story of an isolated, indefensible post, considered one of the most vulnerable in Afghanistan, where soldiers were overwhelmed by the Taliban in a bloody assault years in the making.

When the fighting was over more than 12 hours later, more than half the 53 soldiers at COP Keating were dead or wounded.

Buried in that story is the saga of the uncommon valor of Clint Romesha.

On Monday, he will become only the fourth living person to receive the Medal of Honor for actions in Afghanistan or Iraq.

But on that day, deep in a valley of the mountains of Afghanistan's Nuristan province, it wasn't about a medal.

It was about the men in his section. It was about the buddies he tried to save. It was about the comrades he lost.

In war, heroism is not the intention. But sometimes, it's the result.

'Indefensible spot'

There was little about COP Keating that was comforting to the commander, Capt. Stoney Portis, the platoon leader, 1st Lt. Andrew Bundermann, and the soldiers who made up the Red and Blue platoons, collectively known as Bravo Troop of the 4th Infantry Division's 4th Brigade Combat Team, 61st Calvary Regiment.

By any standard, COP Keating was built in a tough location to defend. It sat on the valley floor, a target for anyone above it in the rugged southern Hindu Kush mountains.

"First reaction was, I think, the same as everyone. You know, this is a pretty indefensible spot," Romesha said in CNN's documentary "An American Hero: The Uncommon Valor of Clint Romesha" that first aired Thursday.

Even the name of the base reflected its harsh surroundings. It was named for Army 1st Lt. Benjamin D. Keating, who was killed when a road leading to the outpost gave way and his vehicle went off the side of a mountain.