What finally drove buck to attack splitz?

Buck was driven to attack Spitz due to a culmination of frustration, rivalry, and the need to assert his dominance. Spitz had consistently challenged Buck's position in the pack, displaying aggression and undermining his authority. The final confrontation was triggered by a moment of provocation when Spitz attacked Buck, prompting Buck to retaliate and ultimately take control as the lead dog. This act was not just a personal victory but also a necessary step for Buck's survival and adaptation in the harsh environment of the Yukon.