What is the theme in The Mask of Command by John Keegan?

By far the main reason to go into any battle is to achieve victory. Alexander got his first real taste of victory shortly after going into battle with Philip II at age sixteen. At age eighteen, Alexander received his first solo major victory at Chaeronea, where he would prove himself as a commander and worthy heir to the throne. Alexander's largest victory by far was over Darius III of Persia, wherein Alexander gained the right to the most powerful kingdom in the world at the time.