During General Sherman’s March to the Sea during the American Civil War, Sherman wrought as much destruction as he could. His goal was to sap the South of both the means and the will to fight. He scoured the countryside for supplies and killed livestock. Rail twisted around trees became known as a “Sherman necktie.” His motto was simple: “War is hell.” Although McNamara would not disagree with Sherman, his fifth lesson is that proportionality should be a guideline in war.

If two things are proportional, they are equivalent or roughly equal. McNamara suggests that damage inflicted in a time of war should be proportional to one’s goals. He does not advocate “taking it easy” on one’s opponents. He is not suggesting a nation fail to get the job done. He is saying we should strive to kill only as much as necessary to achieve our objectives.

In 1945, the United States began bombing Japan using incendiary weapons. 51% of Tokyo was destroyed, killing 100,000. Continue reading →