Complex sentence: ISIS's original aim was to establish a caliphate in the Sunni-majority regions of Iraq, and following its involvement in the Syrian Civil War this expanded to include controlling Sunni-majority areas of Syria.
Split into simpler sentences: ISIS's original aim was to establish a caliphate in the Sunni-majority regions of Iraq. Following its involvement in the Syrian Civil War, this expanded to include controlling Sunni-majority areas of Syria.