Irans role in a major terror attack. New details on the mystery. And scandal at gitmo. The u. S. Base commander is relieved of duty over an alleged affair with a subordinate whose husband was found dead. Im wolf blitzer. Youre in the situation room. The breaking news tonight in the battle against terrorism. U. S. Officials now estimate that Coalition Forces have killed more than 6,000 isis fighters and wiped out half of the top command. Secretary of state john kerry says the allies have halted the terror groups momentum in iraq. That comes a day after we were the first to report that isis has now established in yemen and has been clashing with al qaedas very dangerous affiliate there. And now in a move which could set back u. S. Efforts to combat al qaeda, yemens government, a key ally in the antiterror fight, has resigned after rebel forces seized the capital. Thats raising new concerns about the safety of hundreds of americans in yemen. Our correspondents and analysts are standing by. Lets start with our chief National Security correspondent, jim sciutto. He has the very latest. This is the first time the u. S. Military has put out a hard number on isis losses and it is a big number. The estimated 6,000 fighters killed a significant percentage of the more than 30,000 isis fighters that u. S. Officials believe that isis can muster. Now, we should caution, this is an estimate. Other u. S. Officials i have spoken to stick to thousands killed. Still, it is measurable progress five months into the air war. Kurdish fighters are the offensive today against isis in northern iraq. Now for the first time the u. S. Central command is claiming significant and measurable losses among isis fighters. The result of almost 2,000 Coalition Air strikes, an estimated 6,000 isis fighters killed including half of their commanders. Approximately 1,000 vehicles and tanks destroyed and 200 oil and gas facilities a major source of revenue for the terror group. Almost 2,000 strikes in syria and iraq have had a high degree of precision and accuracy. In recent months we have seen definitively momentum halted in iraq. In some cases, reversed. Reporter military officials caution that the numbers are just an estimate. Defense secretary chuck hagel himself questioned the value of this or any other body count. I have not seen any verification of that number of 6,000 that you refer to. Is that the measurement or a significant measurement of progress. It is a measurement. But i dont think it is the measurement. I was in a war when there was a lot of body counts every day and we lost that war. Reporter still emboldened by coalition gains, iraqi forces are accelerating preparations to retake mosul. Iraqs second largest city, from isis control. Across the border in syria, however, where the moderate westernbacked Ground Forces are still awaiting Coalition Training isis is getting stronger. We have rolled back isis presence from some of the towns in iraq. The same cant be said about syria. In addition to areas where isis may have gained ground in syria, you also have the very disturbing prospect that al qaedas franchise, al nusra, has gained a lot of ground. Reporter isis has an alarming ability to replenish its ranks through recruiting new fighters and those fighters continue to flow in from europe and around the world. Wolf these estimates are based in part on pilots assessments from sometimes tens of thousands of feet in the air, not necessarily 100 reliable but there are other means as well including drone footage and satellite footage. You and i know chuck hagel, the defense secretary. He clearly was not happy that this number was thrown out, not just thrown out anonymously but officially publicly by the United States ambassador to iraq. Thats right, and confirmed with Central Command, Barbara Starr speaking to Central Command as well. Clearly this estimate exists. The question is did the pentagon want an estimate to get out there in public discussion. Also it looks like there is some who will always be skeptical, secretary hagel, chief among them of any attempt to do this reliably. He served during the vietnam war and every day there were great numbers about how many vietcong were killed. That wasnt definitive as far as who won that war. Thanks very much. New concerns about the safety of hundreds of americans in yemen after the sudden resignations of the president , the Prime Minister and the entire cabinet. The move comes after rebels seized the capital, sanaa, demanding a major share of power. Yemen has been a key ally to the United States in the fight against al qaeda which stands to gain from all this chaos. Lets go to our pentagon correspondent Barbara Starr. She is standing by with more. Whats going on . Reporter wolf with the Obama Administration watching this minute by minute now basically the entire government of yemen, the top leadership resigning, president hadi other top officials, some of them saying they just want to wash their hands of the chaos in yemen right now. All of this basically falling apart in the last several hours because that power sharing agreement that everybody thought might work between the regime and the houthi shia rebels really falling apart. No clear understanding now at this hour who is in charge in yemen, who is running the government, and what is really happening there. From the u. S. Point of view the u. S. Assessment still is that the Houthi Rebels pose no direct threat they are not out to attack the u. S. Embassy, they are not out to attack americans, but those streets as you see are extremely unsettled so there remains a good deal of concern about the people who work at the u. S. Embassy to make sure they are safe. I think its very clear that if the u. S. Decides, if the white house and the state department decide that there are just too Many Americans there to ensure everyones safety they will take some of them drive them to the airport, that would be a very typical plan and have them leave the country, try and make that u. S. Footprint, that u. S. Government footprint in yemen, even smaller to reduce the potential risk. Wolf . Because as you know there are a few hundred american diplomats and military personnel in yemen right now, but there are thousands, i dont know how many thousands, we were told by the Yemeni Embassy in washington yesterday, thousands of other americans in yemen right now, mostly dual yemeniamerican citizens. If you have to evacuate all u. S. Citizens that would be a huge job for the u. S. Military. The navy has a couple of ships off the coast but presumably more would be necessary. Well, look in these kinds of situations these socalled noncombatant evacuations when the country is in such turmoil, this is why the state department advises americans early on not to travel to potentially think about leaving a country, try and get the numbers of americans down. If it came to that, it would be a question for the state department on how to get those people out, if the state department would try to charter aircraft to fly them out, if they would try and run helicopters back and forth. There have been in countries in the past there have been any number of ways that they do this. It would be up to the state Department First to make a decision that it wants to take on getting americans out of yemen who want to leave when it is not possible for them to fly commercially. It should be said at this hour the assessment is that the airport remains open and people can still get to the airport safely but you look at those streets in sanaa, the capital, and it does look pretty unsettled. Stand by for a moment. I want to bring in our National Security analyst, peter bergen and chief National Security correspondent jim sciutto is still with us as well. Peter bergen from yesterday to today, now that the entire Yemeni Government is gone for all practical purposes the president , the Prime Minister the entire cabinet, that does not necessarily bode well as far as al qaeda in the Arabian Peninsula is concerned and the concerns the u. S. Has about this terror group. Thats certainly true. President hadi the president who just stepped down as yemeni president , is the first president i think of any country to go to the u. N. And say hey, your american Drone Program really works and he actually gave an interview to the Washington Post saying its a highly effective program. You are not hearing that from many World Leaders and now hes gone. Whoever replaces him is unlikely to have the same attitude. I suspect whoever replaces him will not support, work cooperatively with the United States to continue those drone strikes to try to kill al qaeda operatives in yemen with those hellfire missiles. Its an open question but i think the point is right, to find someone who is as public and open an advocates a real question. Next in line is the speaker of parliament, an ally of the old leader who was pushed out in part by efforts from the u. S. Clearly they wanted this guy in power, hes gone. Its unlikely the replacement will be as open. Certainly, the fact that the now former Yemeni Government was directly helping the u. S. Giving them targets potentially, intelligence information on suspected al qaeda operatives out there, so the u. S. Could launch those drone strikes, im not holding my breath that whoever comes in now is going to be giving the u. S. That kind of information. Im not either. In fact the last drone strike was december 6th. Thats quite a long time. We have seen drone strikes often several a month. The fact theres been a twomonth pause, its hard to interpret but it seems to be related. Let me ask Barbara Starr. Do we know if those drone strikes we just lost barbara for a second. Maybe you know. No. Maybe you guys know. I will start with you. Do we know if the drone strikes, the drones are based on ships off the coast of yemen and fly over yemen, or are they based in yemen itself . I dont think they are based in yemen itself. They are coming from ships, maybe saudi arabia they are coming from other places. There is no drone base in yemen. Its saudi arabia the arabian sea. I have been in that air base and you can see the drones based there like you will see in a place like jalalabad in afghanistan where you have had a consistent Drone Program. At what point, the u. S. Embassy in sanaa, major embassy, very fortified, there is still a lot of u. S. Diplomats, military personnel. We have been reporting at least 100 marines are guarding that embassy. At what point do they start destroying hard drives burning classified documents, getting ready for an evacuation as the u. S. Did in libya, in somalia, in syria and we see this pattern. When they reach an assessment which they havent reached yet that the u. S. Personnel are in grave danger. You heard barbara make the point that the Houthi Rebels were taking over not seen as a direct threat but you have other threats. Just simply the loss of law and order and control is potentially a threat. The first step would be a more calm evacuation. You take commercial flights out under the direction of the u. S. Military. If you had a more sudden collapse you would go the route of sending helicopters from those ships and b22 ospreys from those ships off the coast. We havent reached that state. Thats a dangerous operation, given shoulderfired surfacetoair missiles some of the terrorists have the helicopters going on. They are pretty vulnerable to that kind of attack. Guys, stand by. We are following the breaking news. Much more coming up. Lets take a quick break. Well be right back. Meet the worlds newest Energy Superpower. Surprised . In fact, america is now the worlds number one natural gas producer. And we could soon become number one in oil. Because Hydraulic Fracturing Technology is safely recovering lots more oil and natural gas. Supporting millions of new jobs. Billions in tax revenue. And a new century of American Energy security. The new Energy Superpower . Its red, white and blue. Log on to learn more. Major ok fitness class heres our new trainer ensure active heart health. 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Mr. Chairman, thanks very much for coming in. Lets talk about yemen briefly right now. Are those americans, there are several hundred u. S. Diplomats and military personnel in yemen, and thousands of civilians, mostly dual u. S. Yemeni citizens are they safe . They are at the moment because theyre protected by Yemeni Forces there as well as our marines. The question is who does the commandant for the Yemeni Forces answer to. That is in a state of flux. Because it looks like that whole government is gone for all practical purposes. If these houthi shiiteled rebels if they take charge of the military of yemen, are they going to protect the United States citizens . Thats the big question and at the same time we have just lost our ally president hadi as you know. That ally had helped us mightily in our fight against al qaeda in yemen, so you can bet this is a big step forward for al qaeda. The southern part of yemen has always wanted to break away from control, basically they wanted a caliphate there, al qaeda did, and this is these are some of the concerns. Some of your colleagues angus king of maine, for example, on the senate side has raised fears, get these americans out before theyre taken hostage by some of these terror groups. Yes, we have the ability to do that evacuation on very short, a very short time frame. I was briefed recently on this. We can get our personnel out. We are watching this very carefully. Because we know the u. S. Has at least two ships off the coast of yemen. There are other ships not too far away. I assume that would be the evacuation plan . That is true but at this time we are still trying to bring order out of chaos, still trying to keep the former autocrat the head of the country, from grabbing the reins. Who knows at this point who might end up influencing the outcome. Does the u. S. Even talk to these Houthi Rebels . At this point, they are very close to the iranian quds forces. They were equipped armed, and trained by iran. So those are who they take their marching orders. Because their motto is death to america which they are pretty blunt about that. They have the same motto the iranian guards have used. At least in the short term this looks like a strategic win for iran. Yes, unfortunately in the north its a win for iran in yemen. In the south where al qaeda predominates unfortunately its a win for al qaeda and that particular al qaeda unit of course has been the home of al asari, the bomb maker who attempted several attacks in the United States including recruiting the christmas underwear bomber if you recall. And this is the unit that was responsible if you go through history, the attack on the uss cole. Hes still at large. He is at large. And this is our most toxic, most lethal al qaeda affiliate. Want to move on and talk about isis. One final question on yemen. There havent been many drone strikes lately. With the government gone now, the houthis taking charge is that going to undermine the u. S. Ability to launch drone strikes against al qaeda targets in yemen . Yes, it will because hadi the head of state was particularly helpful with the United States in assisting us in targeting the drone strikes that we were using against al qaeda. He would help provide intelligence to go after ce