They argue because they do not know what they are talking about. There is no way possible they know what happened, the only way you truly know what happened in WWI is if you were in it.
The statement that best describes the outcome of the Persian Wars is “The Greeks were able to stop a Persian invasion, and the Persian Empire stopped trying to conquer Greece.” The problem that led to the start of the Persian Wars was that Persia wanted to punish Athens for the Lomian revolt.
Immigration does not fall under the domestic policy. A domestic policy differs from foreign policy, which refers to the ways a government advances its interests in world politics.