Prior to this paper, no one knew that the Uighurs faced an “epic drought,” Hessl says. The recognition that they did may change the way historians interpret the social, political, and economic strategies of the Uighurs.

Instead of clashing with the Chinese Empire to their south, the Uighurs forged a durable but uneasy alliance with the Tang dynasty in China, a rare feat for a steppe empire. The Uighurs traded their surplus horses with the Chinese in exchange for silk. They then traded that silk with merchant allies in the fertile lands to their west.

“The fact that they had access to a precious and unique commodity might have helped them shore up their economy against the downturn of the drought,” explains the study’s lead author, Nicola Di Cosmo, a historian at the Institute for Advanced Study in Princeton, New Jersey.

The Uighurs’ tenuous alliance with the Tang dynasty wasn’t the only trait that set them apart from other steppe empires. “They were really innovators of how to run a state on the steppe,” says the landscape archaeologist Joshua Wright of the University of Aberdeen, who was not involved in the study. “The Uighurs were the first people who really built big, major cities [on the steppe].”

The Uighurs constructed at least three permanent fortress cities, including a capital that took up about 20 square kilometers. These cities would have served as Silk Road trading hubs.

Their international focus was also reflected in Uighur leaders’ conversion to Manichaeism—a faith that saw the human soul’s internal struggle as a microcosm of an ancient cosmic clash between light and dark—as the official state religion, a conversion likely influenced by foreign merchants at the Uighur court.

The Uighurs’ reinvention of what it meant to be a steppe empire didn’t end there. Archaeological evidence suggests the Uighurs may have been experimenting with farming during the drought, an activity seemingly at odds with their otherwise nomadic lifestyle.

Stefani Crabtree, an archaeologist at Pennsylvania State University who was not part of the study, wasn’t surprised that the Uighurs used trade and diplomacy to support themselves during the drought. “People in the past were highly connected. They had rich social lives and very large social networks,” which is illustrated in the new study, Crabtree says.

Crabtree points out that societies in what is now the southwestern United States also likely used existing trade networks to sustain themselves during long dry spells. And these networks also spanned thousands of miles. For example, medieval pottery with traces of chocolate inside found in Chaco Canyon, in what is now New Mexico, shows that Chaco was part of a trade network that reached to the tropics, where cacao beans grow. These trade networks would have existed during wet periods as well, but it’s likely that trade could have helped offset food shortages. In some ways, the Uighurs’ response to the drought on the steppe may have been the rule, not the exception.