Explain why china was able to isolate itself from western influence until the nineteenth century

Since 15th century, Ming dynasty's foreign policy became increasingly isolationist, which continued on in Qing Dynasty. The main cause of this policy was the raid of south-eastern China from Japanese pirates. In 1723, the controversy between the traditional Chinese rites and Roman Curia escalated. Since that, the government of Qing Dynasty banned all Christian missions in China. According to Kangxi's statement in 1723, he said: "From now on, Westerners should not be allowed to preach in China, to avoid further trouble." This led to the policy of Haijin, which means the the closure of all trading harbours, excluding Guangzhou. However, in late 19th century, the British government started the Opium War in China, and that broke the isolation of the Qing government.