Mu River  Mu River (; ) is a river in upper central Myanmar (Burma), and a tributary of the country's chief river the Ayeyarwady. It drains the Kabaw valley and part of the Dry Zone between the Ayeyarwady to the east and its largest tributary Chindwin River to the west, flows directly north to south for about and enters the Ayeyarwady west of Sagaing near Myinmu. Its catchment area above the Kabo weir is . River flow and rainfall are both seasonal and erratic, at its lowest from January to April, rising sharply during May and June, and high from August to October. Because the Mu lies within the Dry Zone in the rain shadow of Rakhine Yoma, it receives scanty summer monsoon rainfall with a total streamflow of . An old popular expression in Burmese goes thus: "Ma myinbu, Mu myit htin" () - If you haven't seen a river before, you'd think the Mu is it. It may also be called "Mu Chaung" (creek) rather than "Mu Myit" (river) by some. The wooded upper Mu valley is populated by the Kadu and Kanan minorities whereas the fertile lower valley constitutes part of the heartlands of the ethnic majority Bamar. In 1503 Mong Yang Shans attacked and took the northern garrison town of Myedu that guarded the irrigated Mu valley, an important granary to the Bamar kingdom of Ava. These attacks culminated in a full scale invasion in 1524 and the establishment of Shan rule (1527–1555). The Kabaw Valley saw many an invasion by the kingdom of Manipur to the west, most notably during the reign of King Garibaniwaj (1709–1748) when his army crossed over the Chindwin and the Mu, took Myedu, and reached as far as Sagaing opposite the capital Ava. The tables were turned in 1758 after King Alaungpaya ascended the Burmese throne and invaded Manipur. Descendants from Portuguese captives (or "Bayingyi"), taken by King Anaukpetlun after defeating the adventurer Philip de Brito and settled in the area in the 17th century, still keep their Roman Catholic faith. And to this day their ancestry is discernible from their features. The railroad bridge over the Mu river was destroyed by the retreating Japanese forces during World War II. During April and July 1943, USAF B-25s attacked the bridge between Ywataung and Monywa with little success, but accidentally hit upon a method of successful bombing on New Years Day 1944.