However, Chinese historical writers say he was a minister of a local king during the days of warfare (time of Confucius and other philosophers).
Sunzi also had a descendent who was named Sunzi, who also wrote a treatise about warfare. So they might have been the same person.
Anyhow, this treatise has been very influential as a philosophy for winning conflicts. It has become popular in the West as advice to be used in business, and also other competitive activities, like sports and politics.
The text treats war as a kind of “art” to be perfected.