system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What is ISIS' goal?
gpt
They want to restore the caliphate.

The caliphs were both the spiritual (religious) and temporal (military) rulers of Islam. They carved out a huge empire in the first two centuries of Islam, when Arabs conquered the Greek/Roman world across the Middle East and North Africa.

The caliphate became less and less important historically as different Muslim areas broke away, until it was totally abolished in the early 20th century.