【Introduction】
1n 1823, the 3rd year of Emperor Daoguang in the Qing Dynasty, due to sediment disposition, the bed of the Taijiang river became silted up; as a result, two lagoons were formed, which are the Sitsao and Kunshen lagoons. When the Opium War broke out in 1840, Taiwan Garrison Commander, Yao Ying, set up defense positions at 17 ports on the shores to prevent the British troops from invading Taiwan. In addition, to defend Anping Port and the Prefecture City (today's Tainan City), the Sitsao Fort was built on the north bank of the Sitsao Lagoon, forming a horn shape angle with the other five artillery forts of Erhkunshen on the south bank. Sitsao Fort was equipped with 10 weapon platforms, totaling around 99 meters in length. Trenches were dug next to the platforms and bamboo stakes were installed inside the trenches. Outside the trenches, spiked barrels, spiked panels and iron caltrops were deployed. The platforms were mounted with artillery guns, among which two could fire 1500-jin (900 kilograms) shells, three could fire 1000-jin (600 kilograms) shells, and two could fire 800-jin (480 kilograms) shells. Troops and local militia units were stationed to guard the fort. In 1841, during the Opium War, the British captured Xiamen (also known as Amoy) in the battle, and the Ershawan Fort also suffered serious damage. In view of the damage caused by battles, the temporary weapon platforms were then replaced by permanent stone walls.Nowadays, the remains of Sitsao Fort include a 118.6-meter-long artillery wall, which is 1.75 meters in height and 1.25 meters thick. One side of the wall structure is built with cobblestone and mortar and the other side is stacked with granite slabs. The wall has 13 circular embrasures for artillery fire, with an approximate opening of 84 centimeters in diameter, but slightly narrower in the middle of the opening. On top of the wall, between those embrasures, there are roots and veins of old banyan trees twisted and intertwined, indicating how the hand of time has marked the long lapses of ages. Unquestionably, these banyan trees have born witnesses of how Taijiang was once safeguarded.