The Opium Wars were two wars in the mid-19th century involving Anglo-Chinese disputes over British trade in China and China's sovereignty. The disputes included the First Opium War and the Second Opium War. The wars and events between them weakened the Qing dynasty and forced China to trade with the other parts of the world.
In 1820, China's economy was the largest in the world, according to British economist Angus Maddison. Within a decade after the end of the Second Opium War, China's share of global GDP had fallen by half. In another research paper published by Michael Cemblast of JP Morgan and updated by the World Economic Forum, similar conclusions were reached — i.e. China was the largest economy in the world for many centuries until the Opium Wars. In China, the period between 1839-1939 is referred to as the Century of Humiliation.