Re: hoshin1600's tag quotation - Vegetius, like DeSaxe a thousand years later, were "ahead of their time." That's in quotes as they accomplished that by looking to the past, rediscovering what was lost over the ages and reintroducing these martial concepts.
Unfortunately, Vegetius' somber, yet sound advice to the Emperor came too late in history to change the fate of the Roman Empire, while DeSaxe had some success (and would have had much more if he could have avoided so many "wham, bam, thank you ma'am" moments with very powerful women.)
But both men realized that the "old ways" had some keys to success that had been lost to their generation (much like kata), either forgotten, or imitated empty of purpose (what we would call bunkai) Like an important note that has slipped behind the desk, there is useful info to be rediscovered.
Most importantly, they both realized the importance of heart in their troops. Sun Tsu also spent a few paragraphs regarding gauging the morale of friendly as well as enemy troops. A good MA school should take note and not neglect this aspect in training students.