AP Photo/Evan VucciUS Secretary of Defense Ash Carter joined the Chairman of the Joint Chiefs of Staff, General Joseph Dunford, before the Senate Armed Services Committee today to hold forth at great length about the fight against the Islamic State (IS) and all its attendant messiness. The committee, led by Republican Senator John McCain, asked a slew of questions revolving around the central matter of what's happening at the operational level, how it relates to strategic objectives, where all of this is supposed to be going, and how it's going to get there. Carter and Dunford said, in very basic terms, that IS was being squeezed and that progress was being made, but that it's not over yet.