My co-author, Zachary Gochenour, and I have posted our article, “War and Presidential Greatness,” on line here. Here’s the abstract:

Historians and journalists commonly survey other historians on the relative “greatness” of American presidents, and these rankings show remarkable consistency between surveys. In this paper we consider commonalities between highly ranked presidents and compare plausible determinants of greatness according to historians. We find that a strong predictor of greatness is the fraction of American lives lost in war during a president’s tenure. We find this predictor to be robust and compare favorably to other predictors used in previous historical research. We discuss potential reasons for this correlation and conclude with a discussion of how historians’ views might affect policy.

One of the great quotes we lead with is from Theodore Roosevelt, complaining in 1910 after leaving office:

If there is not war, you don’t get the great general; if there is not the great occasion, you don’t get the great statesman; if Lincoln had lived in times of peace, no one would know his name now.

We end with the following two paragraphs:

Woodrow Wilson, by contrast, inserted the United States into World War I. That was a war that the United States could easily have avoided. Moreover, had the U.S. government avoided World War I, the treaty that ended the war would not likely have been so lopsided. The Versailles Treaty’s punitive terms on Germany, as Keynes predicted in 1919, helped set the stage for World War II. So it is reasonable to think that had the United States not entered World War I, there might not have been a World War II. Yet, despite his major blunder and more likely, because of his major blunder, which caused over 100,000 Americans to die in World War I, Wilson is often thought of as a great president.
The danger is that modern presidents understand these incentives. Those who want peace should take historians’ ratings of presidents seriously. Beyond that, we should stop celebrating, and try to persuade historians to stop celebrating, presidents who made unnecessary wars. One way to do so is to remember the unseen: the war that didn’t happen, the war that was avoided, and the peace and prosperity that resulted. If we applied this standard, then presidents Martin van Buren, John Tyler, Warren G. Harding, and Calvin Coolidge, to name four, would get a substantially higher rating than they are usually given.