The verb "fled" in "*He fled from the country" is a transitive verb (verb that denotes an action which passes over from the subject to an object) and has the meaning " ran away from". The preposition "from" therefore is redundant, i.e., not required. The correct sentence should read: "He fled the country."
Some intransitive verbs may become transitive by adding a preposition to them. When you want to show the relation between the action expressed by a verb and a noun, you use a preposition after the verb. Many verbs, when followed by a preposition, take on an idiomatic sense.
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