Taking full account of the factors beyond the control of the U.S. military and avoiding glib comparisons with Vietnam, the author examines how the American approach to the war in Iraq has affected operations there. He also draws on the experience of other nations, particularly the United Kingdom, to identify broad lessons that might inform the conduct of this and future campaigns. He documents the process by which soldiers and Marines in Iraq have adapted to the challenging situation and incorporated both historic and contemporary lessons into the new counterinsurgency doctrine contained in Field Manual 3-24.