About 7,000 terra cotta statues of warriors were buried with a Chinese leader after he died in 210 B.C. (Bigstock photo)

The 7,000 soldiers buried with Qin Shi Huang in 210 B.C. were made of clay. But the bronze weapons the terra cotta army carried into the enormous tomb complex near Xi’an in western China were the real things: tens of thousands of swords, axes, spears, lances and crossbows, all as capable of spilling blood as anything Qin’s real army wielded when they triumphed, ending centuries of war and uniting China under a single rule for the first time.

What has been a puzzle for scientists is how so many weapons could have been made so skillfully, so uniformly and so quickly. (Qin reigned for only 11 years; construction of his mausoleum complex is thought to have started long before his death.) They now have a likely answer. A new study of 40,000 bronze arrowheads suggests they were produced in self-sufficient, autonomous workshops that produced finished items rather than parts that fed into an assembly line of sorts.

Which suggests that something akin to the just-in-time production methods used in industry today may have had a trial run more than two millenniums ago.

“Our initial assumption was that all of these items were mass-produced in large production chains, with the various parts produced in specialized units before they were assembled together. That’s how most cars are made — Fordism, or flow-line production,” said University College London archaeologist Marcos Martinon-Torres. He is lead author of the new study, published last month in the Journal of Archaeological Method and Theory. “However, our data strongly suggest that production was arranged in much smaller units, several working in parallel, each of them sufficiently autonomous and versatile to produce finished items,” or what is sometimes called cellular production, lean production or Toyotism.

While archaeologists who have studied the terra cotta army have long thought that a form of mass production must have been in operation, this is the first time that this assumption has been backed up with such precise data.

The scientists came to their conclusion through metallurgical analysis of the weapons and a statistical analysis of where they were found.

First, they studied some of the 37,348 arrowheads found in 680 locations, using a portable X-ray fluorescence spectrometer, a hand-held tool that determines an object’s precise chemical content.

Although the polished arrowheads seem identical to the human eye, X-ray fluorescence revealed that discrete batches of the copper-tin alloys bore unique chemical signatures. Each batch bore its own mix of copper, tin and lead. Different batches were found throughout the site, suggesting that multiple workshops were operating at the same time.

Then the researchers positioned each artifact and warrior on a digital map based on the detailed records created in the 1970s and 1980s by the Chinese archaeologists who first excavated the site.

An illuminating picture emerged. Each quiver seems to have been produced and assembled by a single workshop. The arrowheads were probably made in batches, tied with linen to bamboo shafts, finished with feathers, bundled into 100-arrow quivers of leather and hemp and placed with terra cotta archers armed with crossbows. (The bows’ organic material hasn’t survived the centuries, but 220 bronze crossbow triggers were found.)

A surprising find

The archaeologists had expected that the quivers’ components would have been produced at a variety of locations and then assembled later. But if that were the case, the arrowheads found together shouldn’t bear the same chemical signature. They should be all mixed up, but they are not.

Finding evidence that the weapons weren’t made in an assembly-line fashion “was a bit of a surprise for us,” Martinon-Torres said. “It was only when we saw this in the terra cotta army that we started to look for modern parallels and found Toyotism.”

“What they did is very sophisticated and convincing,” says Toyotism expert Jeffrey Liker, referring to the researchers. Liker is a professor of industrial and operational engineering at the College of Engineering at the University of Michigan and has written five books on Toyotism.

However, Liker said, the distinction between Fordism and Toyotism in Qin’s weapons workshops was less notable than the fact that characteristics we associate with modern mass production — standardization, quality control, flow — were present at all.

Archaeologists believe that the tomb-outfitting teams were composed of artisanal groups, each of which worked under a master craftsman, with a foreman overseeing quality control. They have identified the seals or signatures of at least 87 foremen on warriors’ backs, indicating a form of personal accountability for the quality of each statue.

No room for error

The statues seem to have been placed in the pit fully outfitted with weaponry because they were so tightly packed in the tomb that there was no room to maneuver around them. This means that the weaponmakers had to coordinate with statue workshops or the flow of work would have stalled, said Martinon-Torres.

Any production problems would probably have been bad news for workers, said Robert Murowchick, director of the International Center for East Asian Archaeology and Cultural History at Boston University. Qin leaders identified who was responsible for each step so that problems in quality or consistency could be tracked to their source “and no doubt punished harshly, as the Qin culture was big on the carrot-and-stick model of management,” he said.

However advanced the Qin manufacturing system was, other modern ideas — such as, say, don’t kill your employees — were absent.

The main historical record that archaeologists rely on for clues to the tomb’s construction is a 1st-century B.C. account by Sima Qian, who wrote that 700,000 people labored to build Qin’s mausoleum complex. Slaves, indentured servants, prisoners of war, foremen, masters, artisans — all were conscripted into a strict hierarchical system with brutal work conditions. Skeletons in iron shackles unearthed at the site back up this account.

Even if the weapons’ makers had high status, it’s likely that some suffered a similar fate. “You don’t want people to have the skills to make these very powerful Qin weapons and then have them disappear and go work for your neighboring state,” said Murowchick.

Murowchick said the weapons production system for the tomb probably mirrored how the real Qin army sourced its weapons and was probably a factor in its battlefield success. “The Qin had a fantastically powerful military by ensuring a standardization of weaponry and also the ability to quickly replace and repair broken pieces on the battlefield,” said Murowchick. “It makes perfect sense to have a cellular production model. If you’re 200 miles from home and need more crossbow locks or triggers or arrowheads, you have teams that can produce things.”

However efficient the Qin manufacturing machine was, Martinon-Torres doesn’t romanticize the megalomania that drove it.

“This was a society ruled by a ruthless autocrat. The mausoleum is a celebration of that super-ostentatious, centralized personality through the sheer investment of manpower and resources,” he said. “We can look at the mausoleum and say, ‘Wow, look how powerful that emperor was.’ But we can also try to reconstruct the hundreds of thousands of anonymous laborers who made it possible. In that sense, we are hopefully giving them a little bit of credit for what they’re worth.”

Pinkowski is freelance science journalist based in Brooklyn.