Portugal, and Chinese pirates
The battle was fought in the Humen Strait, also known as Bocca Tigris (Tiger's Mouth), in the Pearl River Delta. The pirate forces were the Red Flag Fleet of Chinese pirate Ching Shih and her partner Cheung. A flourishing Chinese pirate trade in the area had initially left European traders alone but in 1809 the Red Flag Fleet seized a Portuguese trader travelling from Timor to Macau, which were then both Portuguese colonies, and killed its crew. After her fleet surrendered in February 1810 Ching Shih and Cheung surrendered to the Chinese Emperor, who pardoned them.