Thomas Sutcliffe: Hard steel fist in a terracotta glove

It would be a dull world if all our expectations were fulfilled, so it was intriguing, rather than disappointing, to visit the British Museum's much ballyhooed exhibition of terracotta warriors from the tomb of the Emperor Ying Zheng and find that it wasn't really the statues that stuck in the mind when I left. So what exactly was the expectation in this case?

Well, if one was being obedient to the pre-publicity for the show (and I was in broadly obedient mood on Tuesday) it would run something like this: these are going to be extraordinary objects, conveying an almost eerie sense of human presence across the centuries; they aren't just archaeology, they're art and as such they richly deserve their VIP status, segregated in a specially built exhibition space inside the former British Library reading room. In my case there was also the expectation that there wouldn't be much else besides the warriors – who are billed below the emperor himself in the exhibition's official title (The First Emperor: China's Terracotta Army) but have quite understandably been hogging all the press attention.

I wouldn't want to be blasé about their impact when you do eventually meet them – finally revealed after you've traced a snaking and educative route through the exhibition's ante-chambers. The details are fascinating and the scale of the enterprise (there are estimated to be around 7,000 figures in all) astonishing.

It's true, too, that the detailing is fascinating, with accessories and hairstyles so precisely modelled that a costume designer could reconstruct them without any trouble. It wasn't a bosh job this, and not many shortcuts appear to have been taken. That said, I couldn't entirely suppress some unhelpful analogies as I walked round – "garden ornament" for one, "shop window mannequins" for another. And when I left it was two far more conventional items that left a mark behind them.

One was a bronze sword, made in a government workshop in 232 BC by a worker called Mu, who got to put his name on the blade, not as an assertion of authorship, but so that he could be identified if the work proved defective. Astonishingly, the metal still shines with a golden lustre, the result of an oxidised chrome coating that also appears to have preserved its factory-fresh edge.

It is, given our knowledge of time's power to rust and corrupt, implausibly new looking, a vivid assertion of the technological supremacy of Chinese artisans at the time. The other item is a crossbow trigger – a three-part bronze casting of such precise tolerances that the parts were thought to have been interchangeable. This carries a little more age on it than the sword; it is badged with verdigris at one point. But it shares with the blade an astonishing crispness of outline – the sort of precision we automatically think of as "machine-made".

Both objects have a cutting edge advantage – and they bring home the brutally literal subtext of the metaphor; that the ability to craft a blade that would keep its biting sharpness was one of the great driving forces of cultural advancement, whether you were using it to cut wood, stone or human flesh. Looking at both objects, both military, it's easy to imagine that an arms race is all human culture comes down to – and that art is merely a luxury that only victors can afford. In fact, things are considerably more complicated than that.

Apparently, the tribes that bordered the Qin, who produced these objects, were even more advanced in iron and steel technology, which suggests that it isn't a simple matter of having the best tool. And there are even examples, from other cultures, of a commitment to the cutting edge alone leaving a society vulnerable to attack. In his book Guns, Germs and Steel Jared Diamond cites the instance of the Japanese, who originally took up firearms manufacture with great enthusiasm, perfecting and improving the examples they'd acquired, but later abandoned guns for the samurai sword – an object that sat somewhere between weapon and ritual accessory.

Ying Zheng's secret turns out to have been slightly different – a precision of measurement and production that allowed for mass production. And that's eventually what comes across most powerfully in The First Emperor exhibition – the ruthless bureaucratic efficiency of a society in which human individuality was far less important than collective goals. The objects in its final rooms represent not a triumph of humane vision or creativity, but slightly chilling evidence of a logistical efficiency we generally identify only with the industrial revolution and after. And it all rests on the ability to make mechanisms as precisely crafted as that crossbow trigger – as well as the elaborate quality control that ensures standards don't slip. Despite the individual faces on the warriors it stays with you as a triumph of mass production.