U.S. Pentagon insiders said to be top replacements for Chuck Hagel

In replacing retiring Chuck Hagel, U.S. President Barack Obama must choose his fourth Defense secretary in less than six years and the first who will face confirmation hearings led by a Republican Senate. His nominee will also be presiding over a military much more deeply engaged overseas than Obama ever hoped or imagined it would be three-quarters of the way through his presidency. Even before Hagel’s resignation became official, the names of a pair of longtime Pentagon veterans had already surfaced as top contenders to replace him as secretary: Michele Flournoy and Ashton Carter. While Flournoy has come up through the ranks in policy and strategy, Carter’s experience is in technology and acquisitions.

A big part of being secretary of Defense is managing the largest human institution on the planet, and they are exceptionally well-prepared for that.

Stephen Biddle, an adjunct senior defense fellow at the Council on Foreign Relations

Online supporters of Islamic State have taken to Twitter to cheer the resignation. An Arabic-language hashtag that roughly translates to “IS toppled American Defense Secretary” has been used dozens of times, sometimes alongside images mocking Hagel and the Obama administration. It’s unclear if the social media-savvy terror group actually started the campaign, or if it was the just product of the group’s online supporters.