Pyu city-states
Beikthano ( ) situated in the irrigated Minbu region (near present-day Taungdwingyi) with direct land access to the well-watered Kyaukse plains to its northeast, is the oldest urban site so far discovered and scientifically excavated site. Its remains—the structures, pottery, artefacts, and human skeletons—date from 200 BCE to 100 CE. Named after the Hindu god Vishnu, the city may be the first capital of a culturally and perhaps even politically uniform state in the history of Burma. It was a large fortified settlement, measuring approximately 300 hectares inside the rectangular (3 km by 1 km) walls. The walls and fortifications along it measured six meters thick, and are radiocarbon dated to a period between 180 BCE and 610 CE. Like most subsequent cities, the main entrance of the walls led to the palace, which faced east. Stupas and monastic buildings have also been excavated within the city walls.
Military history of Myanmar
The earliest extant record of warfare in the Pyu realm is the early 9th century when the Pyu states came under constant attacks by the armies of the Kingdom of Nanzhao (from present-day Yunnan). Nanzhao had just become a major military power in the region by defeating the Tibetan Empire in 801. The Nanzhao warriors then pressed down southward into the present-day Shan Hills and into the Irrawaddy valley. Ancient city-states one by one surrendered or were overrun by the "powerful mounted archers from the north". In 832, Nanzhao destroyed the city-state of Halin, close to old Tagaung, returning again in 835 to carry off many captives. The Nanzhao cavalry is said to have swept down all the way to the Bay of Bengal despite stiff resistance.