Improve the grammaticality of this text: Bagan period Following the Nanzhao raids, another Tibeto-Burman-speaking people called the Mranma (Burmans or Bamar), who had come down with the Nanzhao raids, began to settle the central Irrawaddy valley, near the confluence of the Irrawaddy and Chindwin rivers, en masse.
Bagan period Following the Nanzhao raids, another Tibeto-Burman-speaking people called the Mranma (Burmans or Bamar), who had come down with the Nanzhao raids, began to settle the central Irrawaddy valley, near the confluence of the Irrawaddy and Chindwin rivers, en masse.