has been averted for now. >> were korean tensions another cuban missile crisis in the works? it was an unusually tense and busy sunday night at the pentagon. not often the joint heads of the chief of staff worked at the pentagon on sunday night. that's how seriously concerned america was that the situation might escalate out of control. >> the conflict reignited last year when the north shelled yeon-pyeong island the first attack on civilian areas in the south since the 1950-1953 korean war. two south korean citizens and two marines were killed. the u.s.'s 27,000 troops and 50 ships in the region and satellites overhead watching for any north korean troops or weapons movements. tensions rose after south korea announced its intention to stage military drills in the yellow sea. at 10:00 p.m. sunday night admiral mike mullen chairman of the joint chiefs of staff went to work at the high security national military command center deep inside the pentagon. he had two of his most trusted senior advisers on hand all concerned about what north korea's response might be and whether they were going to have to advise president obama to get