Nearly 200 Taliban insurgents attacked the remote American-run outpost near the Afghanistan-Pakistan border on Sunday.
According to the New York Times, which quoted Western officials, this was almost three times the size of the allied force, and naturally took the defenders by surprise.
Nine Americans died in the assault and it took a four-hour battle to drive the attackers back, the paper reports.
The base and a nearby observation post were held by just 45 American troops and 25 Afghan soldiers.