How the Terracotta Army Was Made, and What It Still Guards

The Terracotta Army was made to guard the man who first unified China, the emperor Qin Shi Huang, after his death in 210 BC: roughly 7,000 life-size clay soldiers, officers and horses, equipped with real bronze weapons and buried in battle formation in pits east of his tomb. Building it was an imperial project in its own right, with clay prepared centrally, figures assembled from parts and finished by hand, and weapons turned out in batches. The emperor himself still lies beneath his burial mound, which has never been opened.

Why did China's first emperor need a clay army?

Qin Shi Huang, born in 259 BC, came to the throne of the state of Qin as a boy and completed the conquest of its rivals in 221 BC, creating the first unified Chinese empire. He imposed a single script, currency and system of weights and measures, and he joined older frontier walls into the defenses later remembered as the Great Wall of China. Work on his tomb began in the 240s BC, soon after he took the throne, and went on until he died. The result is a funerary complex modeled on his capital, Xianyang, with the burial mound at its heart inside two rectangular walls. Archaeologists have found more than 600 pits, tombs and graves of tomb builders across a site of about 56 square kilometers. The army stands about 1.5 kilometers east of the mound, facing outward, away from the tomb, as if watching for enemies. Estimates of the workforce behind the whole complex run as high as 700,000 laborers and craftsmen. It stayed hidden for more than two thousand years. In March 1974, villagers from Xiyang in Lintong district, near Xi'an, were digging a well when they hit fragments of pottery figures. More than a year of survey and test digging revealed Pit 1, which measures 230 by 62 meters and is thought to hold about 6,000 figures and horses. Pit 2, an L-shaped pit with an estimated 1,300-plus figures and horses and a richer mix of troop types, turned up in April 1976. The small Pit 3, with 72 figures and horses, followed in May; some scholars see it as the army's command post.

How do you mass-produce 7,000 soldiers?

The figures were made close to where they stand. A 2017 study in the journal Antiquity examined the clay under the microscope and found that it was processed centrally and then shared out to local workshops, with sand mixed in, probably to make it easier to shape and tougher once fired. Stamps, inscriptions and painted marks on some statues point to several different workshops. Some had been thought to lie in the capital, Xianyang, about 50 kilometers away, but the clay study found no sign of that and placed production in the local Lintong area. Exactly how the bodies were built is still debated. Perhaps the most widely accepted account has the head, hands and torso made separately and then joined, with heads and hands pressed in molds and torsos shaped by hand. Another view has every part cast as a separate module. Zhang Wenli, a researcher at the site museum, argues that the legs were solid clay and the upper body was built up in coils, with arms, hands, ears and heads taken from molds. A team in Xi'an tested the question by rebuilding warriors from scratch. They coiled strips of clay and concluded that the whole body could be made in one piece, with only the head separate. Every version agrees on the finishing stage. A layer of finer clay went over the rough form, and craftsmen carved it into hair, beards, eyes, armor plates, belt hooks and leg bindings. That is where the army's famous variety comes from. UNESCO describes the figures as all different, yet the individuality was layered onto standardized, partly molded bodies, and most scholars doubt that they were portraits of real soldiers. Last came color. Each figure received one or more coats of lacquer before painters added natural and artificial pigments such as cinnabar, bone white and synthetic barium copper silicates. The bare gray army in modern photographs is what remains once that paint is gone.

Were the soldiers' bronze weapons rust-proofed?

The army was armed for real. The partial excavation of Pit 1 alone has produced dozens of spears, lances, swords and hooks, more than 260 crossbow triggers and up to 40,000 bronze arrowheads, many of them in bundles of 100, the load of one quiver. Those weapons were mass-produced too. Study of the triggers suggests they came in batches, perhaps held in an arsenal, with each batch issued to the crossbowmen of one section of Pit 1. Chemical fingerprints of the arrowheads suggest they came not from one production line but from a cellular system of small, multi-skilled teams that still achieved remarkable consistency.

The metal's condition gave rise to a modern legend. Many blades emerged shiny and sharp, and for some forty years a theory circulated that Qin smiths had protected them with a chromium-based anti-rust coating. In 2019, a team led by the archaeologist Marcos Martinón-Torres put it to the test. Of 464 weapon parts scanned, only 37, about 8%, carried detectable surface chromium, and it showed up mainly on parts that had rested against lacquered wood or bamboo, such as sword grips, scabbards and lance shafts. The lacquer, not the smiths, was the source. The real preservative appears to be the burial soil, a moderately alkaline loess with a pH of 8.1 to 8.5, very fine particles and little organic matter. In an aging experiment, bronze buried in that soil stayed close to pristine after four months at 60°C and 90% humidity.

Why has the emperor's tomb never been opened?

At the center of the complex, the burial mound still rises 51.3 meters. Sima Qian, the Han dynasty historian born around 145 BC, described workers from every province laboring until the emperor's death to build an underground city inside it. He also wrote that the chamber reproduced the empire in miniature, with the heavens shown above and its great rivers and sea imitated in mercury that machinery kept flowing. Nobody has gone in to check. After about 50 years of surveys and excavations across the wider complex, the burial chamber itself remains unexcavated. In 2007, The Art Newspaper reported that there were no plans to excavate the mound. Jiao Nanfeng, then director of the Shaanxi archaeology institute, said Chinese law prohibited excavating the graves of emperors, while the museum's director, Wu Yongqi, spoke of respect for ancestors and stressed that protecting the relics and the site came first. The pits show why caution makes sense. Excavation there has been slow and intermittent, and only a little more than 2,000 warriors had been dug out by 2019. Once exposed, even fired clay faces new threats: in 1999, environmental experts quoted in the China Daily warned that nine kinds of mold were attacking the figures, helped along by the warmth and humidity of visitors' breath. The Terracotta Army is less a mystery than a record of how the first Chinese empire worked: central supply, standard parts, local workshops and batch production, all aimed at one man's afterlife. Like the pyramids of Giza more than two thousand years earlier, it shows a state's whole logistical machine bent to a single ruler's tomb. The difference is that the man it was built for is still sealed inside, and his country has chosen, for now, to leave him there.