After a war, all parties turn to “lessons learned,” a phrase that has become commonplace. A war is, in a hideous way, a learning opportunity, with the goal being that the successes and failures of one’s own forces are identified and the process that led to either outcome is studied and integrated into planning and training for the next war. This is altogether reasonable and necessary. It is also obvious that the process is an occasion for finger-pointing: Taking credit for another’s victories or shifting blame for defeats is an inevitable part of the learning process, not to mention the promotions process. Officers are human like the rest of us. A more troubling aspect of the learning process is that the war gets elevated to revealed truth, and sometimes guides nations to future defeat, the past towering over all the changes that have rendered the lessons learned not only useless but catastrophic. Napoleon’s infantry charge was much valued in 1914, with leaders initially unable to grasp the meaning of the machine gun.