I think you’re underplaying the sequel aspects. Russia was one of the antagonists in the first installment, began as an antagonist in the second, but flipped to protagonist ally in the first act. Also in the first installment the Ottoman Empire was an antagonist ally, where Turkey was neutral through all of WWII. Finally, China was an ally in WWII and huge victim of the Japanese , but underwent a revolution joining with Russia to become the primary antagonists in the third installment “Cold War”.