Answer:
In the Second Opium War, the Brits forced the issue by invading the Chinese port towns of Guangzhou and Tianjin (1857–1858).
Why did the UK start the Opium War with China?
It was indeed a dark, ugly and wicked history for the UK and the West and a miserable, disastrous memory for billions of Chinese, which should never be forgotten, never forgiven by everyone in the world.
At that time, China had plenty of world-renowned, top-notch nice things, like china, silk, textiles, spice, and arts, tea …, which had been desperately dreamt of and avariciously coveted by the West, including the UK. On the contrary, at the same time, the UK and the West had nothing or only very few that held much interest and attention to hundreds of millions of Chinese for them to offer and supply, what the UK sufficiently had and was shamelessly able to suffice to the world was only poisonous, addictive opium equipped with its imperialistic gunboat diplomacy to invade and colonize other countries. Massive smuggled opium by the UK had been used to poison, exploit and poverty hundreds of millions of Chinese in the nineteenth century, therefore these greedy UK opium smugglers and drug dealers made skyscrapers full of dirty money at the cost of millions of Chinese future, health and lives.
Undoubtedly, the unscrupulous UK’s opium smuggling and subsequent China’s defeat in the Opium War had grossly led to China’s calamity-ridden, heartrending one hundred years in the 19th century and early 20th. Such dark and painful history has been tremendously, constantly motivating and pressing billions of people in China to work hard, fight hard and create nowadays unprecedented China’s rise marvel.