The first thing you need to recognize when you are reading an English translation of Sun Tzu’s The Art of War is that you are dealing with what former US Defense Secretary Donald Rumsfeld called “known unknowns”. Scholars are not certain about when the book was written (estimates range between 770 BCE and 221 BCE), whether it was written by one or several authors, and what motivated the author(s) to write the book.
Bertrand Russell, a philosopher possessed of a razor-sharp analytical mind, once said that he didn’t want to write about Confucius because he found the Chinese philosopher “boring”.
There’s much to be said for attempting to develop social and political theories, models and philosophies based on something other than Western lines of thought and datasets; the latter’s universality and applicability to the wider world is something which, if not taken merely on faith, that needs to be demonstrated. China, with intellectual, political and social histories of its own, offers both alternatives to, and tests of, prevailing Western conventions.
The Earth may be divided among many countries, but since there is only one Heaven, there can be but one tianxia, or “all-under-heaven”. The Chinese concept tianxia might be literally translated into English as “sky-beneath”, and it has been variously rendered as “enlightened realm”, “world-system”, or simply “the world”. To keep Chinese scholars happy, just don’t translate it as “empire”. The West had empires. China had tianxia.