When President Trump’s trade team presented Chinese officials with a list of bold economic demands in Beijing last May, one of China’s state-controlled news outlets, Global Times, panned the request and blared a curious headline: “Is it now 1840?”

Five months later, China’s national news agency, Xinhua, accused Vice President Mike Pence of lacking knowledge of China’s past after he complained that Beijing was merely paying lip service to opening its economy.

Behind the pushback is a long and painful history of China surrendering to Western powers, with origins in what the Chinese news media refers to as a “century of humiliation” that began with the “unequal treaties” of the 19th century after the first Opium War.

History has been haunting trade negotiations between the world’s two largest economies, which have dragged on for more than a year. While the administration’s requests surrounding forced technology transfer and subsidies of state-owned enterprises remain unresolved, the deepest division centers on the United States’ insistence of an enforcement mechanism that gives it power to impose tariffs if China abrogates its end of a trade agreement.