European agriculture was quite sustainable until the appearance of fossil fuels and mined fertilizers in the middle of the 19th century... French population had been more-or-less constant since the Celtic era, at that point, with rises due to more efficient use of the soil's productivity, and two population dips due to systemic (but not necessarily caused by agriculture) crises.

And wars of conquest aren't exactly unknown in China, either.

Un roi sans divertissement est un homme plein de misères