for more about that, we're joined by janine davidson, a senior fellow at the council on foreign relationso the president has said repeatedly, no boots on the ground. here we have an aircraft carrier off the coast. does that mean drones are likely, or aircraft launched from these carriers? >> it means options. an aircraft carrier can do an array of things from intelligence to air strikes. >> in these sort of densely populated areas, are we likely to incur greater civilian casualties if we don't have people on the ground? >> that is the greatest risk of air strikes and why some people think they're not a viable option. you need people on the ground calling in where those things are going to happen, especially in an urban environment. now, if there are areas where the enemy is in an open space and you can confirm, then it may be more viable. >> so in these open spaces, if i'm marching down that major highway towards baghdad, does that make them more visible to these drones? >> sure, if i was a military planner for isis, i would think that's a risky way to go, but it may be their only option.