The art of War is a book describing strategy. The major key components are as follows:
Deception, is the first main key strategy that is stressed in this book.
Deception can be things such as: fooling your opponent, getting into his ranks, earning his trust and so forth.
The next is command, how you treat your soldiers and get them to follow you throughout battle as well as keep their loyalty. A famous quote from Sun Tzu is, "Lead by example, not by command."
The last thing is calculations, knowing the terrain on which you march on, the enemies next moves, the time you have, when you can strike, where you should strike. This is extremely important to winning a war.