Kishimoto was horrible at creating a coherent timeline. Constantly Retconning events and changing history.
We know nothing about any of the First Three Great Ninja Wars. When they started, who was involved, how long they were. Or how long were there periods of peace between the Wars.
Even things like when Tsunade left the Leaf village is confusing. Did she leave after the Second War when Dan died? Or after the Third, since she knew about Naruto before they met. Even Kishimoto doesn't know.
We know nothing about any of the First Three Great Ninja Wars. When they started, who was involved, how long they were. Or how long were there periods of peace between the Wars.
Even things like when Tsunade left the Leaf village is confusing. Did she leave after the Second War when Dan died? Or after the Third, since she knew about Naruto before they met. Even Kishimoto doesn't know.