good morning, john. reporter: good morning, rob and vinita. at the white house, president obama was awakened and told shortly before 4:00 a.m. tuesday. white house spokesman robert gibbs says the u.s. is firmly committed to the defense of south korea. it was the heaviest attack since the korean war ended in 1953. north korean artillery shells rained down on south korea s yeonpyeong island, killing at least two soldiers, wounding troops and civilians alike and setting dozens of houses ablaze. south korea returned fire and scrambled its fighter jets. south korea was carrying out an annual military exercise when north korea protested and warned them to stop or face retaliation. then, north korea fired. the island houses about 1,000 south korean marines and 1,500 civilians, mostly fishermen. the attack occurred days after three stanford university scientists returned from a visit to north korea s yongbyon nuclear facility, saying the north korean nuclear program was far more advanced tha