yemen, home base for al qaeda's arabian affiliate. u.s. officials say the government there is on high alert. at least a dozen tanks are deployed near the u.s. embassy. some u.s. military forces are on a higher state of readiness, and officials say the threat is greater than it's been in a long time. cnn's becky anderson is standing by in abu dhabi. jim acosta is at the white house. we begin with our pentagon correspondent barbara starr on that higher state of readiness within the u.s. military. when did it start? i assume i know why. tell me the decision-making process. >> candy, what we have learned is it was earlier this week as the threat emerging, defense secretary chuck hagel began sharing chairing a series of high level meetings in the pentagon, saying where do we have troops, what can we do? there are marines on duty in southern spain, southern italy, and in the red sea. hagel ordered that they be on the highest possible state of readiness. this is something the military doesn't take lightly. they've done it before. how ready can they be?