Widely seen as both the father of the modern American way of warfare and its most formidable practitioner, Ulysses S. Grant remains an enigma more than 150 years after the guns of the Civil War fell silent. More than 200 biographies of Grant have been published since his death in 1885, including two major recent scholarly biographies and a flurry of other works since 2000. Virtually every month, a serious book on the Civil War is published, and most of them make at least a modest attempt to take the measure of the most famous man from Point Pleasant, Ohio.

What made U.S. Grant tick? What explains his remarkable strategic insight into the war that took more American lives than all the conflicts we’ve fought in since the beginning of the 20th century combined? Why did the Great General and Savior of the Union turn out to be such a mediocre president?

The truth, I think, is that we really do not know, and probably never will.