Short fiction about a planet with two sentient species, one having enslaved the other one

Question

I read this novelette at least 40 years ago, in a collection, in English, which was most probably the original.

It describes the first contact between humans and the natives of a planet they just discovered. Human explorers first managed to get some basic knowledge of the language and customs by observing the natives from space with electronic devices. There were two related but distinct species, and one of them had totally enslaved the other one, though the number of the slaves was vastly superior. They had very limited technology, about hunter gatherer, I think, maybe a bit of agriculture.

Once they got those basic facts, humans made first contact. In the beginning, everything seemed to go well. The local chiefs of the dominant species agreed to exchange various local products for human low-tech implements which were very high-tech for the natives.

At some point, something went wrong. The leader of the human expedition felt the atmosphere had changed, but he did not understand what had happened. He also did not expect the vicious ambush the natives had prepared. They killed a few humans and wounded many more, but they did not fully understand the powers of the high-tech human weapons and despite their huge numbers (the slaves fighting alongside their owners) they were defeated and had to flee.

Then something went right again. Some local chiefs came to the humans with apologies and asked them to resume exchange of goods. Again the humans did not understand what had happened, so they said they had go home to tend the wounded and would come back.

When back to civilisation (I'm not sure it was on Earth, maybe just in any human inhabited planet, or space station) the leader met with some friends, maybe also with the top brass of the organisation. They did a "post-mortem" of the whole story to understand what went wrong and what went right again, so they could return without going through similar tragic episodes. IIRC, the explanation of both changes of attitude of the natives was found. The humans concluded that they could go back, now that they knew what to do and what to avoid at all price. Alas, I don't remember what it was.

Answer 1

The Master Key by Poul Anderson

This is one of three stories in Trader to the Stars (1965), though apparently much of it was published earlier in Astounding Science Fiction. The story is framed as a debrief by Nicholas Van Rijn, with Per Stenvik and his ensign Manuel Felipe Gomez y Palomares recounting what happened to his trading mission to Van Rijn and two other guests.

The dominant race are the Yildivans, with Lugals as the related, completely obedient slave race. Per tells the story of how there are initially good relations between the Terrans and the Yildivans. However, Per attempted to discuss religion and also made it clear that he was acting on the orders of his superiors in the trading company. This is where things went sideways, with a subsequent major Yildivan assault (using melee and muscle-powered weapons) that was annihilated by Terran firepower. Per was injured in the attack, but was heard to give an order to Manuel which was subsequently disobeyed.

It was the disobedience that was the critical behaviour that restored good relations. Van Rijn deduces the psychology of the Yildivans and their relationship with the Lugals - the very short version is that initially the Yildivans were treating the Terrans like themselves, then became hostile when Per's religious and organisational discussions made the Terrans seem more like Lugals (unworthy of respect). Manuel's insubordination was something impossible for the invariably obedient Lugals, restoring the Terrans to the status of being equivalent to Yildivans and worthy trading partners.