Buck stands up to Spitz in chapter 3 and defeats him after Spitz attacks him for the third time during a rabbit chase. After defeating Spitz, Buck trots to Spitz's former position as lead dog. However, Perrault and François decide to put Sol-leks into the coveted position, which upsets Buck. Buck knows that he has earned the position of lead dog and pounces towards Sol-leks several times. Eventually, Perrault and François relent and allow Buck to lead the sled. Buck excels as a lead dog and is by far the most talented lead dog Perrault and François have ever seen. Buck's leadership skills are unmatched, and he motivates the other dogs to push themselves like they've never had before. Buck punishes Joe, forces Pike to give maximum effort, and the entire group recovers its solidarity with Buck as their leader. Buck is so effective as a lead dog that his team breaks a record for the fastest run from Thirty Mile River to Skaguay.

After Buck stands up to Spitz and beats him in a fight to the death, Sol-leks is made the lead dog.  Buck repeatedly challenges him too, and is finally allowed to lead the team.  Under Buck's leadership, "the general tone of the team picked up immediately...it recovered its old-time solidarity", and the team makes record runs, averaging forty miles a day for fourteen days (Chapter 4).  After a short time of celebrity, the exhausted team is capriciously sold to another handler to run the mail from Dawson to Skagway.