Who wrote the book used as the lead text formalised as the Seven Military Classics?
The Art of War:  For almost 1,500 years it was the lead text in an anthology that would be formalised as the Seven Military Classics by Emperor Shenzong of Song in 1080. Sun Tzu:  Sun Tzu is traditionally credited as the author of "The Art of War", a widely influential work of military strategy that has affected both Western and Eastern philosophy.
Sun Tzu