All of them. Sun Tzu wrote about competition in terms of a mental competition, a mental comparison of competitive positions. He not only understood that all current weapons and methods would be outdated, but he made the idea an underlying principle of his system.
The only weapon he deals with is the human mind and how it works in competitive situations. His work is more properly a work of the psychology of “dominance hierarchies” than a work of about military conflict.
One important lesson in studying his work is that human psychology has not changed in the last 2,500 years and will not change in the next 2,500.
I wish I could list all of his relevant insights, but the list is currently around over 230. See a list of articles here.