Complex sentence: On 20 September, ISIS forces reached to within 15 kilometers of Kobane after capturing more villages overnight in fighting that left 18 ISIS fighters dead, while more than 300 Kurdish fighters reached Kobane from Turkey as reinforcements.
Split into simpler sentences: On 20 September, ISIS forces reached to within 15 kilometers of Kobane after capturing more villages overnight in fighting that left 18 ISIS fighters dead. At the same time, more than 300 Kurdish fighters reached Kobane from Turkey as reinforcements.