Barack Obama will bequeath to his successor the two wars he inherited from his predecessor. At least in the near term, that unwelcome fact will define his legacy as a statesman.

As a candidate for president back in 2008, Obama had promised, if elected, to end the Iraq War and to win the war in Afghanistan. He failed on both counts. In retrospect, the expectations—his own and ours—that he would make good on those promises appear embarrassingly naive.

Elect a rookie to fill the most powerful post in the world and you get rookie mistakes, with American soldiers paying in blood to educate their commander in chief. Bill Clinton’s education came in 1993, when a recklessly conceived nation-building project in Somalia came precariously close to replaying Custer’s Last Stand. The education of George W. Bush commenced precisely a decade later in Iraq, when an even more recklessly conceived stab at regime change produced an epic quagmire.

Like Clinton and the younger Bush, the callow Obama arrived in the Oval Office largely unschooled in the arts of statecraft. For advice and counsel, of course, he, like they, recruited a coterie of impressively credentialed “wise men” (and women) ostensibly well versed in the ways of the world and the workings of government. Yet résumés do not necessarily connote actual wisdom; when it comes to decisions, presidents are on their own.

Once in office, Obama wasted no time addressing the two wars that were now his. And with reason: Concluding the US interventions in Afghanistan and Iraq on some approximation of favorable terms formed the condition for pursuing his far more ambitious goal, enunciated in his June 2009 Cairo speech, of making “a new beginning between the United States and Muslims around the world.” As long as US forces occupied Muslim-majority countries, no such new beginning was likely to occur. ...