Learn Turkish: O gizli üs hemen boşalttırıldı mı? - Was that secret base ordered to be evacuated immediately?

The base verb here is boşaltmak (to empty or evacuate). First, we add the causative suffix -tır to make it "to have [it] evacuated." Next, we add the passive suffix -ıl to make it "to be ordered to be evacuated." Finally, we add the definite past tense suffix -dı.

What is the exact difference in meaning between saying boşaltıldı and boşalttırıldı?

Boşaltıldı is simply the passive form, meaning "It was evacuated." By inserting the causative suffix to make boşalttırıldı, you emphasize the chain of command: someone in authority caused or ordered the evacuation to happen. It translates best as "It was ordered to be evacuated."

Wait, isn't the -t at the end of boşaltmak already a causative suffix?

Yes, good eye! The root is the adjective boş (empty). It becomes the intransitive verb boşalmak (to become empty). Adding -t makes it transitive: boşaltmak (to empty something). So when we add -tır, we are actually using a second causative suffix to mean "to make someone empty something" before finally making it passive.

Why does the causative suffix use -tır instead of -dır, creating a double 't' in the middle of the word?