The name of the ferocious tribe was the "Yeehats." The attack occurs in Chapter 7. Buck comes upon the maurading band:
"The Yeehats were dancing about the wreckage of the spurce-bough lodge when they heard a fearful roaring and saw rushing upon them an animal which they had never seen before. It was Buck, a live hurricane of fury, hurling himself upon them in a frenzy to destroy....It was a fateful day for the Yeehats. They scattered far and wide over the country and it was not until a week later that the last of the survivors gathered together in a lower valley and counted their losses. As for Buck...he found Pete where he had been killed...Thornton's desperate struggle was fresh-written on the earth..."