The Dagu Forts , also called the Peiho Forts are forts located by the Hai River (Peiho River) estuary, in Tanggu District, Tianjin municipality, in northeastern China. They are located 60 km southeast of the Tianjin urban center.
The first fort was built during the reign of the Ming Jiajing Emperor between 1522 and 1527. Its purpose was to protect Tianjin from attack by wokou sea raiders.
Later, in 1816, the Qing government built the first two forts on both sides of the Haihe estuary in response to increased concerns about seaborne threats from the West. By 1841, in response to the First Opium War, the defensive system in Dagukou was reinforced into a system of five big forts, 13 earthen batteries, and 13 earthworks. In 1851, Imperial Commissioner Sengge Rinchen carried out a comprehensive renovation of the forts, building 6 large forts: two on the south of the estuary, called "Wēi" and "Zhèn", three to the north, "Hǎi", "Mén" "Gāo", and the sixth, the "Shitoufeng" Fort, was built on a small ridge on the northern shore. Each fort had 3 large guns and 20 small caliber guns. Forts were constructed of wood, brick and an external curtain of two feet of concrete, the layering designed to avoid spalling and minimize artillery rounds' penetration. The forts were around 10 to 15m high, which located as they were in an exceedingly flat landscape, provided a critical vantage point.