First Battle of Chuenpi
1840 British victory

The Battle of the Barrier was fought between British and Chinese forces at the boundary separating Macao from the Chinese mainland on 19 August 1840 during the First Opium War. Located in modern-day Portas do Cerco, the Macao Peninsula was connected to Xiangshan Island by a narrow isthmus about 100 m (330 ft) wide and 1.2 km (0.75 mi) long. A wall called the Barrier was built across the isthmus in 1573, and it served as Macao's border.