Lincoln faced a very steep learning curve when the war started. But Lincoln was a quick study. He had taught himself to be a lawyer. Learning military strategy proved to be something else he could do very well. He read books on strategy, military history and learned from the successes and failures of his troops in the field. He also learned from the enemy's military tactics. He learned so well that by 1862, historian T. Harry William said about him: "Lincoln stands out as a great war president, probably the greatest in our history, and a great natural strategist, a better one than any of his generals." Although there is no evidence he ever read Karl von Clausewitz's "On War", his actions followed the book's central argument: "The political objective is the goal, war is the means of reaching it, and means can never be considered in isolation from their purpose. Therefore, it is clear that war should never be thought of as something autonomous but always as an instrument of policy."