By the early 4th century the kingdom of Kush, which used to control much of Sudan's riverbanks, was in decline, and Nubians (speakers of Nubian languages) began to settle in the Nile Valley. They originally lived west of the Nile, but changes in the climate forced them eastward, resulting in conflicts with Kush from at least the 1st-century BC. In the mid-4th century the Nubians occupied most of the area once controlled by Kush, while it was limited to the northern reaches of the Butana. An Aksumite inscription mentions how the warlike Nubians also threatened the borders of the Aksumite kingdom north of the Tekeze River, resulting in an Aksumite expedition. It describes a Nubian defeat by Aksumite forces and a subsequent march to the confluence of the Nile and Atbara. There the Aksumites plundered several Kushite towns, including Alwa.