Violence can break out anytime. Three quarters of the troops are close to the heavily armed dmz. Its because of the joint military exercises happening now with the United States and south korea. They began on monday and go until august 28th, next friday. Here is a time line of whats been unfolding. August 4th, a land mine exploded, injuring two south korea soldiers. They are denying they placed the land mine. August 10th, south korea was broadcasting propaganda with large loud speakers. Saturday, north korea threatened indiscriminate strikes and sent a warning letter on thursday. Thursday afternoon, thats when both sides traded fire. North korea launching a rocket. They responded with 36 artillery shells. Today, kim jongun saying he is ready put troops in a wartime state, south korea warning to retaliate. It appears now, chris, that the situation is only escalating. We have heard this rhetoric before, this is particularly sensitive and a dangerous time. Will, thank you for setting the scene for us in terms of the provocations. The question now is will south korea concede to the norths deadline by tomorrow morn sng lets check if with kathy novak near the dmz. What do we know at this point . Reporter chris, it seems the short answer is no. South korea is refusing to stop the propaganda broadcast and preparing for further escalation. South korea will strongly retaliate if there is additional provocation from north korea and south korea is expecting there will be. North korea is very, very angry that south korea has restarted the campaign of psychological warfare, using the propaganda speakers along the border. North korea, as we know, likes to tightly control the message it gives citizens and with south korea broadcasting its own messages. North korea threatening to blow up the speakers. Its culminated the tensions that seem to be getting worse as the deadline approaches and, of course, as we know, this is happening as the United States and south korea hold joint military exercises, Something Else that makes them extremely angry. Thank you so much for that. The u. S. , as kathy mentioned is monitoring the conflict between the nations. Lets get to Barbara Starr who has the latest for us in washington. Barbara, good morning. Good morning, michaela. The pentagon is going to continue the exercises with south korea in a number of nations in the region. The exercises designed to send a message north that the u. S. And the South Koreans are ready to respond if north korea were to stage an attack. Behind the rhetoric we are talking about, the u. S. Intelligence community looking forward to reality. What is political theater and what is the actual military reality on the ground. U. S. Satellites will be scouring for any indications of north korean troops on the move, but also very critically, all the back ups they would need. Food, fuel trucks, ammunition, resupply. They have a lot of artillery near the border. They can absolutely stage an attack on almost no notice at anytime they want. If hes talking about putting his troops on the war footing, he has to feed them, provide fuel and he has to provide ammunition resupply. Quickly, critically, the North Koreans expert add deception. They have been moving to bury much weaponry underground. They can bring it out and use it very quickly, very difficult to detect. This is a big challenge for the u. S. Intelligence community. Alisyn. It sure is. Thank you for explain thag. Lets get more context. We bring in arthur chang. Gordon, great to see you this morning. North korean troops mobilizing at the border. What does this mean . It means this is the way a war can start. This is what it would look like. Its not to say there would be war. I think north korea could do a number of things to surprise the South Koreans and us. We could see detonations of bombs in seoul or Something Like that. Nonetheless there is probably going to be something terrible. The reason is, inside the north korean regime there is turmoil. King jongun executed two fourstar generals this year. Theres been a lot of fighting among him and army officers. That cant be a good thing in connection with what we have seen the last four or five days. Its ominous you believe something terrible will happen. They are known for saber rattling. You think this is beyond that . Im sure it started out as bluster and saber rattling. They created a dynamic of their own. The problem for kim jongun is he may not be able to back down. I dont think hes irrational. Hes unpredictable. Hes unpredictable by north korean standards. Im not sure he knows what he wants to do. Because of the severe fighting at the top where we have seen 85 Senior Officers and officials executed since he took over in december, 2011, because of this infighting, i think theres all sorts of things that could happen and probably will. North korea has given south korea a deadline of 4 00 a. M. Our time to stop the messages they are broadcasting over the loud speakers. Is that the answer . Can it be deescalated if the south stops the messages . If the south stops the messages, it could deescalate. On the other hand, it could escalate things because kim jongun realizing he can push them around may try to get further advances. He wants to bolster his legitimacy and his standing among military officers. Nothing is better than that that one success after another. I dont know what the answer is in this particular case. Its going to be consequential one way or the other. Two south korean soldiers were injured by land mines. They were severely injured by land mines in the dmz. Was that an accident or was this the north provoking them to begin with . This certainly was not an accident. One thing we have to remember is that north korean soldiers have been infecting recently and maybe they planted the mines to prevent their own mines from preventing their own soldiers from going to the south. What we have is two fatalities among south korean soldiers. That sort of limits what seoul can do. There have been deadly incidents in the past in 2010 where south korea did not react. That led to further incidents. Im referring to the sinking of a ship. South korea did not retaliation. That led to the shelling of a south korean island in november of that year. Four people dead, two of them civilians. There is an escalation here. Im not sure jim jongun knows how to play it skillfully. His father played it skillfully. His grandfather did. Im not sure kim jongun know what is he is doing. How do they handle it . Normally, we get on the phone to beijing and say bring in your allies. Kim jongun in 2013 started a process of cutting his ties with china. He killed his uncle who was responsible for relations with beijing. He executed one of the fourstar generals i talked about because that general refused to cut ties with beijing. So, basically, what we have is a situation where north korea is on its own. We really dont have any pull with the chinese and the chinese dont have pull with north korea. What are the u. S. Options . The u. S. Options are to convince the North Koreans we will destroy them if they engage in a full scale mobilization and war across the dmz. Its deterrence at that point. We dont have any other options. Just couldnt be more dire sounding. Gor dan, we appreciate what you have give us. Thank you. Lets shift to the 2016 race. Forget the, its too early part. It is not too early for a strategy shift. Thats what we see in the gop right now. Donald trump and jeb bush are separating from the pack and they are now clearly focusing on each other. The big headline for you this morning is out of florida. Trump is now leading the former governor, the Florida Governor, jeb bush among republicans in bushs home state. Cnns athena jones is live in New Hampshire on the campaign trail with the latest. He had his first town hall up there, trump. Now hes headed to alabama where they say they were forced to move it to a football stadium because so many people want to come. Reporter thats right, chris. Its getting more and more interesting. Jeb bush is getting help from his big brother, the former president sent out a fund raising email telling supporters jeb has a tough road ahead. If your strength and support, he will succeed. This comes as jeb is facing his biggest hurdle, yet, donald trump, who is drawing huge crowds. Its the summer of trump. They are calling it the summer of trump. Reporter the donald trump tour is making its way from the northeast thank you. Thank you. Reporter to the south today. Hosting friday night pep rally in mobile, alabama, boasting the largest crowd, yet. 30,000 to 40,000 people in alabama. Reporter hes been known to exaggerate his numbers. Outside, sadly, we have thousands of people that cant get in. We have a lot of people outside, hundreds and hundreds of people standing outside. Reporter perhaps this time, the proof is in the tickets. Tonights event has been relocated, twice. It was first set to take place here in the civic center theater, occupancy, 1900. Then the larger arena, occupancy, 10,000. Now, at least 35,000 claimed tickets. It will kick up the turf here at this high school stadium, capacity, 43,000. Meanwhile, one of trumps leading rivals getting unwanted questioning after using a phrase many consider offensive in a radio interview this week. Anchor babies. Do you recent using the term anchor babies . I dont. I dont regret it . You dont . No, do you have a better term . Im asking you. You give me a better term and ill use it. Serious. Dont yell at me behind my ear. Sorry about that. Hillary clinton how about babies, children or american citizens . An uncharacteristic befence for bush similar to trumps unapologetic use of thephrase on wednesday. What else would you like to say . Undocumented immigrants. Ill use the word anchor baby. Excuse me, ill use the word anchor baby. Reporter one more point about that term, anchor baby. The center right Leadership Network, jeb as one of the advisers said in a 2013 memo to avoid the term anchor baby because its offensive. Michaela . All right, we are not going to hear the last of that anytime soon, thank you. President obamas Approval Rating declining in a new cnn orc poll say 47 say they approve of how hes handling the job down from 49 . 38 approve of how hes handled the u. S. Relationship with iran and support calling 56 of people say congress should not approve the agreement. But the president is trying to shore up more support for the iran deal this morning publishing a new oped across the nation and writing a letter to congress. Jimmer carter revealing that cancer, first discovered in his liver spread to his brain. Carter scaling back his work as he begins radiation treatment. We are live in washington with the latest. Reporter it was an extraordinary press conference. President carter was warm, open and really seems to be at peace with his future. I was fortunate enough to interview him several times in atlanta and he is the same, straight forward, generous with his time. Hes describing it as a new adventure in gods hands. A rare and personal moment, out in front for the world to see. They think they have it all. Its in four places in my brain and likely to show up in other places in my body as the scans detect in the future. Reporter thurs, president jimmy carter received radiation treatment after doctors removed cancer from his liver. His regimen, radiation and drugs to boost his immune system. His family has a history of pancreatic cancer that killed his brother and two sisters. Ill be prepared for anything that comes. Reporter the 90yearold georgia peanut farmer, who became the 39th president is reflective about his life. The best thing i did was marry. Thats the pinnacle of my life and we have had 69 years together. Still together. So, thats the best thing that happened to me. Reporter carter said his biggest regret was he was unable to free the hostages in iran on his watch. I wish i would have sent in more helicopters to get the hostages. I would have been reelected. [ laughter ] that may have interfered with the foundation of Carter Center. Reporter then, if he had to choose. If i had to choose between four more years and the Carter Center, i would choose the Carter Center. Reporter i asked him about the big picture. What would you like to be remembered for in terms of your legacy . We always told the truth. We kept our country at peace. We put peace to other people around the world. We promoted human rights and never deviated from that. Those are some of the things im proud of. The Carter Center, the former first couple traveled the world for the past three decades doing humanitarian work. He would like to travel to nepal for habitat to humanity, hes going to put his treatment first. He plans on Teaching Sunday School this weekend as he does every sunday. Chris . People are getting exposed to the authenticity you have come to expect from president carter. It is not easy to talk about what hes talking about right now. Doesnt matter that hes older or done so much, it takes a lot of strength. Thank you for giving perspective on him. A window of what hes about. Theres a child poet. Hes since left us. One of his dreams was to meet jimmy carter because hes a humble peacemaker. We contacted him. He said send me the poetry. President carter is a poet. He said this is good stuff, i want to meet him. Calls him up, goes on gma and talks to him about peacemaking. He had no motivation except whats in his head and heart. He is a good man. So sweet. So sweet to hear him talk about his wife. Lifelong love affair. Breaking overnight. Underground explosion rocks a highrise. Fire trucks, emergency crews, crowding the boulevard. At least five people suffering minor injuries. The blast likely caused by a generator on the ground floor. The building received structural water damage. More to come. This explosion at a high school last night. It was so powerful it felt like an earthquake. Crews are working on a gas line on the sixth floor at the time. We are told three construction workers were seriously injured. Investigators are trying to pinpoint the cause of that explosion. Donald trump from outside without a chance to now it seems his rivals can only hope to contain him. The republican frontrunner prepping for his biggest rally, yet. Its going to fill a football stadium in alabama. Our panel will weigh in on whether anyone in this field can beat him. Assuming yes, how . It takes a lot of work. To run this business. But i really love it. Im on the move all day long. And sometimes, i just dont eat the way i should. So i drink boost® to get the nutrition that im missing. Boost complete nutritional drink has 26 essential vitamins and minerals, including calcium and vitamin d to support strong bones and 10 grams of protein to help maintain muscle. All with a great taste. I dont plan on slowing down any time soon. Stay strong. Stay active with boost®. But your stellar notebook gives hanyou the gumptionlc. To reach for the sky. Thats that new gear feeling. This week, these Office Depot Brand notebooks just one cent. Office depot officemax. Gear up for school. 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Needing a football field. Its such a big event, he needs a stadium that holds 43,000, hype or proof of the populous momentum . Trump okay, i think its both, first of all. Its very trump to move something to a stadium. Alabama is a place where the trump voter lives. Someone who may be a lot more conservative than the average voter. Someone who agrees with the immigration policy. I can see why there would be a lot of interest, particularly in alabama. Jason, lets talk about this. The biggest number before this was Bernie Sanders in portland, oregon, 28,000 people turned out for his campaign. If trump gets 35,000 as he says thats the number of tickets asked for. What does it mean . Maybe not a flash in the pan or hes a showman and at some point things will level out . I think hes certainly a showman. He has yet to show and sanders has yet to know they can translate the crowds to people that turn out and go to caucuses and primaries. Thats going to be a challenge to get people who show up to go and volunteer. You need an organization. He doesnt have that right now. He has drawing power, so does sanders. Its summer, people want something to do. I think this High School Football stadium will probably fill up with people. They want to see the show when the circus is in town. They will check out trump. Jason, thats one side of it. Jackie, lets take the other side of