Complex sentence: During the First Intermediate Period the Egyptian presence in Lower Nubia disappeared, and when Egyptian sources again mention the region at the beginning of the New Kingdom, they report Kerma in control of both Upper and Lower Nubia.
Split into simpler sentences: During the First Intermediate Period, the Egyptian presence in Lower Nubia disappeared. When at the beginning of the New Kingdom, Egyptian sources again mentioned the region of Kerma, they reported Kerma as in control of both Upper and Lower Nubia.