Not so much grimdark as it is epic in scale. People forget that China once had 1/3 of the entire earth population at one point in time.

It makes everything that involves them, from wars to execution, just that more dramatic in my opinion.

If you want grimdark, you should look at the Mongols and what they did.

They used Chinese peasants as meat-shield when they face the Chinese armies. Their commanders and chinese archers hesitate from firing their bows, allowing the Mongols to close the gap.

Mongols used diseased cattle and dead peasant bodies into heavily-dense urban cities and use said disease to force the population into capitulation.

Perhaps one of my most favorite grimdark that the Mongols did was when they invaded Eastern Europe. To test the loyalty of those they subjugated, a lone Mongol warrior would go to each village or hamlet and is allowed to do whatever he wishes upon the populace, even killing random people. This is their way of testing the loyalty of their subjugates. If they raise their hand in response, the Mongols would raze the village to the ground.

Well soldiers eating civilians and eachother is pretty grimdark, also I already knew about the Mongols using corpses for biological warfare.