this morning new daletails the crisis in yemen. more than 500 houthi rebels have been killed. more than 200 air strikes in two weeks. a saudi source tells cnn that saudi arabia is using u.s.-made apache attack helicopters in some areas. meanwhile, hundreds of yemenis are calling it a violation of international law. let's bring in cnn military analyst retired major general major "spider" marks. how likely do you think of a ground invasion and how would that change this equation as we see these protests in the streets? >> i think, number one, saudi wants to make sure it can at least protect its integrity so it has forces, obviously, disappoint deployed along the border why wyemen. it would be some trigger event