Learn Turkish: Devlet, beklenmedik baskın üzerine gizli dosyalara el koydu. - The state confiscated the secret files upon the unexpected raid.

In this structure, üzerine means upon or as a result of. It can follow a bare noun or a possessive construction. Here, baskın üzerine means upon the raid. Using the bare noun treats the raid as a general triggering event. If it were a specific, previously discussed raid, you might see the possessive chain baskının üzerine, but the bare noun is extremely common in news and formal reports.

How exactly is the adjective beklenmedik built?

It comes from the verb beklemek (to wait or to expect). It takes the passive suffix -n to make beklenmek (to be expected), followed by the negative suffix -me and the past participle suffix -dik. Literally meaning that which was not expected, it has become a fixed, everyday adjective for unexpected.

Why is dosyalar (files) in the dative case as dosyalara?

This is driven by the verb phrase el koymak, which means to confiscate or seize. Because it literally translates to putting a hand to something, it requires the target of the action to take the dative case.

Why is there a comma immediately after Devlet?

In written Turkish, it is a standard punctuation rule to place a comma right after the subject if there are many words between it and the verb. This immediately clarifies who is performing the action, preventing ambiguity in longer sentences.