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PAULA ZAHN, CNN ANCHOR: As we mentioned, since mid-afternoon yesterday, America has, indeed, been on high alert. The government is responding to what it called a "credible threat."
Let's go to Bob Franken, who is standing by at the Pentagon this morning to find out exactly why we're in this state, and how we found out we got there.
Good morning -- Bob.
BOB FRANKEN, CNN NATIONAL CORRESPONDENT: Good morning, Paula.
And there's sort of an accumulation of reasons. First of all, there has been an ongoing interrogation of people around the world, people who have been captured by the United States since the war on terror. There has been the analysis of all of the so-called chatter, the radio transmissions, telephone transmissions, that are intercepted by the United States.
And there came a point the night before last that the belief was that there was a credible threat, probably most likely against U.S. facilities overseas. But it was unspecific enough -- if you'll pardon the term -- that they decided that they needed to ratchet up the alert here. And of course, they did pick it up a notch to where we are now at a high concern about some sort of terrorist activity.
You pointed out a moment ago that there are missile batteries around Washington. We're not going to tell you exactly where they are, but we can tell you what they are. They are Avenger armed missile batteries that could be used to repel an attack.
This is the first time that we have had this in the United States, where missile batteries, armed missiles, have surrounded Washington since the Cuban missile crisis in the '60s. So, of course, that gives us pause.
What also gives us pause is what is going on behind us and what has gone on. A year ago, almost exactly a year ago now, the building was aflame. There was a 50-foot fireball, some people say, when American Airlines 77 crashed into the building; 184 victims, 189 died, including the terrorists who were on board.
The building, of course, has been completely rebuilt. It was an act of defiance, considered a miracle. But it was also quite miraculous, people said, that the Pentagon so quickly rebounded and almost immediately continued its normal operation, an operation that has continued over the year, and we have seen the result of it. The result: the war on terror.
But this is a day to pause and remember. At 9:37, there is going to be a moment of silence. That is just about the time that the plane hit a year ago.
Then, there is going to be a tolling of the bells. That's going to be preceded, actually, by the unfurling of the giant flat that quickly went up on the site of the Pentagon when the rebuilding began almost immediately after the plane had hit.
Then, we're going to hear speeches from President Bush, Defense Secretary Rumsfeld and the chairman of the Joint Chiefs of Staff, Richard Myers.
All of that to mark the day, which is a day to look back as the Pentagon spends most of its time looking forward, planning its various war on terror. And of course, now, there's a lot of focus on Iraq.
So, it's going to be a day to remember -- Aaron.
AARON BROWN, CNN ANCHOR: Bob, thank you.
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