In the Call of the Wild Buck feuded with Spitz from the first day he joined the dog pack, his main problem with Spitz started after Spitz laughed when Curly was brutally attacked by a large group of huskies. Throughout the book both Buck and Spitz have been open with how much they dislike the other, however it was Spitz who would constantly act on it making Buck angry, because Spitz was the pack leader and Buck was a relatively new dog he couldn't do anything to prevent Spitz from harassing him.Spitz would constantly steal Bucks sleeping locations and food as well as try to start a fight whenever
he could. However Buck knew enough to wait to have his fight with Spitz. During this fight Buck fought smartly and patiently, eventually beating Spitz and earning his spot as the leader of the pack. When Buck became the leader of the pack he pushed his fellow dogs to the limit by running as far and as fast as everyone in the pack could go, it left the pack with a sense of contempt.
After Buck successfully beat Spitz in their fight and became the leader of the pack he treated the rest of the dogs very well, as well as attempt to help the other dogs when they joined him when he was with Hal, Charles, Mercedes.
The rest of the dog pack was scared of Spitz, so after Buck beat him and became the new leader the rest of the pack was able to relax and focus on their performance.
An example of this is after Spitz is killed each dog is able to focus on really relaxing when they are done running for a day, instead of worrying about what they will do if Spitz steals their food or warm sleeping spot, or even start a fight.
Buck was a better leader of the dog pack than Spitz was because he was able to bring out the best in his fellow dogs as well as return peace to the pack, examples.