For instance, the Spanish Civil War is seen as a precursor to World War II, but it isn’t considered a part of World War II because different sides supported different belligerents, including direct military action, the conflict remained in Spain.
This is part of the reason why NATO nations have not provided direct military action to support Ukraine, as it would lead to a likely escalation to World War III.
Major powers in direct conflict with each other.
For instance, the Spanish Civil War is seen as a precursor to World War II, but it isn’t considered a part of World War II because different sides supported different belligerents, including direct military action, the conflict remained in Spain.
This is part of the reason why NATO nations have not provided direct military action to support Ukraine, as it would lead to a likely escalation to World War III.