Thomas Ricks NEW YORK TIMES   If the best measure of a general is the ability to grasp the nature of the war he faces, and then to make adjustments, George Washington was one of the greatest the United States ever had. This is not perceived even today because he had few victories during the entire War for Independence. But it was not a war that would be won by battles. It was a different sort of conflict. Washington came to understand this, and he changed, moving away from the offensive strategy that was natural to him. Washington adjusted, while the British did not. And that made all the difference.   Thomas Ricks is the military history columnist for The New York Times Book Review and a visiting fellow in history at Bowdoin College. Before becoming a full-time author, he covered the U.S. military for the Washington Post and the Wall Street Journal for 25 years, receiving two Pulitzer Prizes as part of reporting teams at those newspapers. He is the author of six books, including Pulitzer finalist Fiasco: The American Military Adventure in Iraq, 2003-05. His most recent book was Churchill and Orwell: The Fight for Freedom. He is married to Mary Kay Ricks, author of Escape on the Pearl.