As protests spread across the Arab world in late 2010 and early 2011, the Obama administration struggled to decide a strategy. Torn between sticking with the autocratic strongmen who had long been America's allies or democracy-seeking protesters on the streets, it lurched one way and then the other, only rarely committing completely to an outcome.

How much influence Washington ever had over events in the region remains an open question. Obama's most decisive action — to intervene militarily in Libya to oust Moammar Gadhafi — unquestionably defined events there, although the unending conflict and instability since were hardly the preferred outcome.

In Egypt, the United States ultimately did nothing to stop the military regaining power, while in Syria support for those attempting to oust Bashar Assad was never more than lukewarm. Only when it came to defeating Islamic State was the U.S. truly committed militarily, and events of last week suggest that under President Donald Trump even that can no longer be taken for granted.