In 1974, a group of farmers were slowly digging a well in Xi’an, China, when one of them hit something hard with his shovel. As he continued to dig, he realized he had discovered an ancient clay statue.
Archaeologists knew that China’s first emperor, Qin Shi Huangdi, had an underground mausoleum somewhere in the area. But the mausoleum had been intentionally hidden after his death in 210 BC, and guardians planted trees on top in hopes he would never be found. But when archaeologists began to investigate, they realized the clay statue was one of thousands buried just below the surface.
Called the Terracotta Army, there are no other burial sites who compete with it underground army. And in recent years, new technologies have helped scientists understand how they came to be. Archaeologists have even discovered 20 more Terracotta Warriors in 2022.
Scientists have yet to dig up all of the soldiers buried with the Emperor, but they estimate as much as 8,000 statues make up this army of clay. The statues were buried in three separate pits and include life-size warriors, officers and horses.
The warriors wear uniforms which distinguishes them from officers. Horses wear harnesses and chariots have wheels with dozens of spokes. Some of the tanks are covered but have an open window, others are open to the sky and have an umbrella to protect the driver from the sun.
The soldiers were positioned in a battle formation, protecting the Emperor in the afterlife. Scientists believe the workers started creating the clay army when Qin Shi Huangdi ascended the throne at age 13 in 246 BC.
Learn more about the Terracotta Army:
As king, Qin Shi Huangdi spent 25 years fighting and taking control of warring states. Once he unified China, he declared himself the first emperor. His dynasty ended just four years after his death, but the landmass over which he ruled remained unchanged for centuries.
Some archaeologists believe it took up to 700,000 craftsmen and laborers to build the army over the years and production stopped when the emperor died in 210 BC They worked for nearly 40 years to build the army and experts suspect that many of these workers were slaves who were executed once their services were no longer needed.
Many mysteries surround the clay army, and in recent decades new non-invasive technologies have helped scientists understand how the clay army was formed.
Build an army
Researchers used remains found among the statues to determine the material used to build the army. In a study 2017 in Antiquity, scientists examined 12 fragments from warrior statues in Pit 1, which is the largest of the three pits. They also examined samples of cobblestones and other statues, such as a figure representing a palace acrobat.
They discovered that the statues were made of a non-calcareous clay paste which could have come from the loess deposits, a type of siltstone common in northwest China. The Acrobat and Warrior Fragments also contained sand tempering, meaning the sculptors changed the recipe at some point.
Read more: The 6 Most Iconic Ancient Artifacts That Continue To Captivate
Non-invasive technologies have allowed researchers to better understand the production process. In a study 2021 in Archaeometrythe researchers used portable X-ray fluorescence spectroscopy to see inside the statues.
X-rays revealed distinct marks on the statues, “Gōng” (宫) and “Xianyang” (咸阳). They believe these are the names of the two workshops responsible for making the clay army. The names help explain variations in clay sources and distinctions in clay paste.
Although the warriors were made from terracotta, the bronze weapons they carried were both real and well preserved. For years, scientists have wondered if the designers intentionally used a rust preventative to protect the bronze.
In an article from 2019 in Scientific reports, the researchers were curious about the chromium detected on the bronze and whether it was intentionally used to preserve the weapons. They analyzed samples of the weapons and the soil in which they were buried. They discovered that a lacquer had been used to coat the clay warriors and that it was rich in chromium. Over time, the lacquer mixed with the earth and the chrome spread over the bronze weapons.
Even though the chrome coated the bronze, researchers did not believe it was responsible for preserving the weapons. They suspect the bronze resisted due to the soil having a moderately alkaline pH and small particle size.
The Terracotta Army was supposed to defend Qin Shi Huangdi in the afterlife, and now the warriors have their own protection. The the site has been added to the United Nations Educational, Scientific and Cultural Organization’s World Heritage List in 1987, and a government-run museum manages and monitors the excavations as they continue.