the pentagon acknowledging it doesn't agreement with the iraq government to send in those advisers, but insisting they are certain they will get one. >> we're pursuing something in writing. the second is absolutely committed to making sure our troops have the legal protections. and he would not do that on a nod and a wink. >> reporter: for now, the first troops will be drawn from those already in the country. as the fighting rages, u.s. officials already know plenty else could go wrong. one senior defense official telling cnn the whole mission is not without risk. if the legal problem is resolved, some u.s. troops will go to northern iraq, the stronghold of isis sunni militant fighters. how much will small numbers of u.s. special forces really be able to see? and the big concern, u.s. troops are not supposed to be in combat, but what if they are