One of the first items on the Secretary's agenda during a surprise visit to Afghanistan Monday was to meet with the troops.

As he met with young service members at Bagram Air Field an airman asked him, "What keeps you up at night?"

Gates was composed at first. "What keeps me up at night?" Gates repeated, joking that he got that question in front of Congress last week.

But quickly his face turned. He trembled and said, "I would tell you that you all keep me up at night."

Gates said he thinks often about the Americans in Afghanistan, the sacrifices they've made and "the friends they lose." "After four and a half years on the job, that's what keeps me up at night," Gates said as he fought back tears.