fomore about this, we are joined by anthony cordesman of the center for strategic and international studies in washington. cordesman previously served in the state department and was the director of intelligence assessment in the office of the secretary of defense. >> sreenivasan: so what happened in the past few days? >> what happened is that a combination of syrian and iraqi kurdish forces, backed by u.s. and other airpower, opened up a line where yazkis-- these are a minority group who have been stranded on a mountain range for months-- could actually move out along the ground. now, this was impoant not only because the yazdis for the first time were given a secure ground route to escape, but there are estimates up to 8,000 kurdish troops were involved, that they were able to make effective use of air support, that this is the largest operation so far as an offensive ground-air operation against the islamic state. >> sreenivasan: so strategically it's iortant because they are able to maintain control of a region? >> well, it's important because they were able to operate a significant gro