I just read this from Wikipedia's article on Mongolian military tactics:

When Mongols slaughtered the whole population from settlements that resisted or didn't opt to surrender, they often spared the engineers and other units, swiftly assimilating them into the Mongol armies.

"Engineers" in this case meant people who could build trebuchets and catapults and other siege machines. (It might also mean metalworkers, woodworkers, glassworkers?)

How did they screen such people from the population? Did they have translators who could speak their language, and if so, where did they get those translators?

And especially, how did they test liars (I'm an engineer, don't kill me!) from truth tellers?

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    The last one seems easy enough. Have the guy perform his craft. If you don't like the results, too bad for him. I'd be interested in seeing the historical answer though. May 26, 2017 at 13:02
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    "other units" is likely the key here. They are talking about entire units in opposition armies, and sparing the engineering units. They aren't talking about random citizens in conquered cities.
    – T.E.D.
    May 26, 2017 at 13:28
  • @called2voyage Building a siege engine takes a lot of time and resources and work. Building something quick from wood might not be a great test either, because I would guess even an illiterate peasant would know what to do with a saw/ax. Perhaps they would judge by the rough or smooth finished form, but that still seems a tedious test to screen the entire city population with.
    – DrZ214
    May 26, 2017 at 13:30
  • @DrZ214 Yes, my comment doesn't adequately cover the full scope of the thing, but I think it points in the direction of what sort of technique they might have used. May 26, 2017 at 13:32
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    @DrZ214 Battlefield medicine might comprise another unit that could be coerced to do work. May 26, 2017 at 13:45

4 Answers 4


First, as explained earlier, the language and customs of enemies are not totally new to Mongols. Second, if you referring to engineers specifically, then it was the Jin (Chinese) dynasty that they learnt siege-craft from. The battles with Jin dynasty had many, many defections (Chinese to Mongol) of senior officials. So, it would have been straightforward after that for Mongols to identify these Chinese engineers. In fact, in the very first battle against the Jin dynasty, at Yehuling, the Chinese emissary defected! Clearly, their reputation preceded them.

Finally, and this is only for context, they did not always kill off everyone in the bigger towns/cities because they needed the population for trade and taxes. As you read in the Mongolian military tactics, their army was in fact extremely disciplined (their reputation notwithstanding). Hence, the Chinese engineers could still volunteer or join up with the Mongols after the dust has settled.

On sources, for Yehuling, the defection is stated in the Wikipedia article. On not killing off everyone, the sources are in almost all recent historical research. For instance, this is from chapter 4 - 'The rule of the infidels: the Mongols and the Islamic world', 'New Cambridge History of Islam' (Cambridge University Press, 2010), first paragraph:

"The Mongol period was a watershed for the Islamic world, as it was for most of Eurasia. The ferocity of the conquest and the confusion of early rule exacerbated an agricultural decline already deepened by decades of internal warfare. For artisans and merchants, however, the period brought significant new opportunities." (emphasis mine)

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    Sources would improve this answer.
    – MCW
    Jul 8, 2017 at 21:55
  • I think this is the best answer here. Thank you for posting it and welcome to the site. You seem to know a lot about Mongolia Empire. I can't find any good online sources (in English) about Mongolian Empire other than Wikipedia. Wikipedia is a good start, but just a start. Things like Roman Empire get way more attention in the western world, which is a real shame. Mongolia dominated Asia and was the largest land empire, and you would think we are beyond bias in the 21st century, but theres very little about it even in Youtube docs. Sorry for the rant but I really do feel starved for this.
    – DrZ214
    Jul 9, 2017 at 0:09
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    Thank you for the welcome. Yes, there is more research now but it has yet to 'hit' Wikipedia. Hopefully, it will soon.
    – J Asia
    Jul 9, 2017 at 6:36

The obvious answer would be that the Mongols, like all states, could easily persuade or coerce their conquered subjects into becoming collaborators. These collaborators can then provide essential services like translation or screening.

As an example, in an early conquest, Genghis captured the Naiman Tata-tonga, who was originally a scribe within the Naiman Khan's court. He was not only well-versed in languages, but invented the Mongolian script, adapting it from the Uyghur alphabet. This script was highly successful and is used by many ethnic Mongolians to this day. So it's quite easy to infer that the Mongols acquired other translators and experts in a similar fashion.

Another example is Guo Kan, a Han Chinese general who (or more accurately, whose master) defected to the Mongols when they invaded Jin, commanded artillery units which were involved in many famous Mongol sieges, including Baghdad and Xiangyang.

The Mongols were not aliens who materialised out of thin air; their tribes had been in contact with neighbours speaking different languages for centuries. This contact means there will have always been a need for translators.

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    +1 for the example, but I find the final paragraph slightly misleading. Existing translators for neighboring regions makes sense, but the Mongols expanded so rapidly and so extremely far away that acquiring translators had to be a concern.
    – DrZ214
    May 29, 2017 at 5:53
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    Even if you weren't neighbours, you can get translators from their neighbours. It's the "I know a guy who knows a guy" thing. May 29, 2017 at 5:55
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    In terms of familiarity of custom and languages, I would explain the point via the Turko-Mongolic tradition. They have traded, fought and formed alliances endlessly since ancient times (since Xiongnu tribes from 3rd century BC). As for familiarity with military doctrines and technology, the Xia (Tanguts) - Liao (Khitans) and Song dynasties were falling in and out of each other against the Mongols, cf. afe.easia.columbia.edu/song/out/rivals.htm
    – J Asia
    Jul 10, 2017 at 18:20

The most likely way, assuming a language barrier, was by observation. That is, they captured people in the process of operating the enemy's anti-siege machines (which would be similar, though not identical to siege machines). Or people at workshops manufacturing articles of glass, wood or metal. In the case of doubt, they would test the candidates, see how they worked, and if the end product "stood up."

Put another way, the Mongols wouldn't necessarily "screen" the whole population for candidates. They would pick out the obvious ones, that is people who were clearly doing work in engineering, or whatever they wanted done. Or, as another poster pointed out, they would select someone they already knew by reputation. The idea of making "direct contact" with the population is a fairly recent one, going back perhaps to the 19th century. Ditto for "Yellow Pages" listing people by occupation.


Very simple. They just commanded: "engineers, please come out of the crowd". Those who did not move were either killed or used on low qualification jobs, like human shields in the sieges of fortified places. Those who did come out but then turned out to be poor engineers were also killed, perhaps with more pain (Mongols especially did not like those who lied).

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    I realize this may be an area to which you have devoted some study, but this community requires a little more explanation (preferably with sources) as to where this information came from. May 26, 2017 at 19:05
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    As of right now, I haven't downvoted, but this answer comes off as speculation taken to be trivial/obvious, when in fact without sources it should not be considered either. At best, this answer is a possible method. If it stays that way then I think, and please don't take this the wrong way, that it's worthy of downvote.
    – DrZ214
    May 27, 2017 at 13:48

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