Transcript for Syrian conflict explained: Simple questions for a complicated conflict

Hey everybody on the live in New York so check this out by now. You will have seen some earlier in your news feed or in your headlines. Just how bad things have gotten in the war Siri just yesterday president trump. Made headlines by changing its stance we're hearing from Syrian officials now with allegedly. A chemical attack. Earlier in the week but information is hard to come high they were gonna try to walk through how we got here in the first place. Joining me live now from our London bureau is ABC news his own Alex Moore art with been covering this conflict. From the beginning and it's gonna help explain what's going on Alex thanks so much for taking the time. Thanks for having me we're gonna try we're gonna try our best it's a complicated topic I should warn everyone watching at their summit the images. You are about deceit are pretty graphic. And if you've seen any of these in your news feed it will be no surprise to you so Alex. Let's start at the beginning a good place to start a lot of people focus on what's happening now in some of the horrific images and videos were seen. If they're something we can point to as a starting point con. We could talk about this for several our honors outbursts quite honestly this is an extraordinarily. Complex war. That people often called a Syrian civil war but that implies that it's really just Syrians fighting against Syrians which six years later couldn't be farther from the truth. This now. Is a truly international war which is taking place essar which involves a very complex web of players were from Syria from the surrounding Arab countries from the rest the Middle East and beyond Europe and the US. Now this started just over six years ago not long after we saw uprisings in Tunisia and Egypt and in Libya. The story goes that a group of school children in the southern Syrian city of Tehran were chanting slogans calling for the fall of the Asad regime a same slogan that we heard. In other countries that had seen uprisings as well the children were then arrested and tortured. 1000 march 2015 and that led to protests in their raw peaceful protests which then spread across the country. Or rather than engaging in talks the regime of president Bashar Assad crackdown and very harshly which then ignited. This armed and violent uprising now fast forward six years later to now can kind of break it down to three major camps that's really simplifying it. There's the regime whose army has been depleted and seen mass defections and it that's now being propped up by Iran. By the Lebanese militant group Hezbollah and most notoriously by Russia. They're fighting against crisis and the rebel groups and there's ices which declared its so called Khaled patent when he fourteen and of course is fighting against everybody. The regime the rebel groups and being bombed by the US led coalition. Then you have the Syrian opposition the rebel groups of which there are hundreds some of them backed by the US some by Turkey some by Saudi Arabia and other gulf countries. Summer extremists like the al-Qaeda offshoot. And all the while you have the battle in the sky the US led coalition with its fighter jets sharing that airspace over Syria with the Syrians. And the Russians so like we said it's incredibly complicated and at this point hardly what you. Call a civil war. It's nearly impossible to unravel but let's talk about what we know the fact has been. So far because sometimes we get the information in drips and with various events. Overall what do we know about how many people have been killed or injured along the way. Well it's been just over 48 hours so far in the numbers have of course changed since this attack. And because this is such a hard place to get to and western Syria they're different. Sources that are reporting different figures are right now according to a leading watchdog group called western observatory for human rights. Close to ninety people were killed more than half of whom. Are women and children we've seen that horrific video and pictures coming out of the victims many of them children. And many of them just in sense there are multiple reports saying. Hundreds more have suffered from the effects of what is universally being described as a nerve agent. Meaning that the death told could rise because so many are still in critical condition. Now if you mentioned how difficult it is to get information from there we have to rely on a lot of the groups with a proven record of credibility. But let's back it up a little bit on the specific chemical attack backing 2013. This hearings agreed to give up all the chemical weapons right. And then then secretary John carrying 2014 said that there were no more chemical weapons there so how would this attack have been carried out in the first place. Yeah let's go back three and a half years ago to the summer of 2013 this all started really went with president Obama's famous red line comment that we've heard so much about. Threatening military action if chemical weapons were used in Syria. More than 1000 people were killed in a chemical weapons attack outside Damascus in August of 2013. And as president Obama's administration was considering military action as we saw this fierce debate taking place. Someone a reporter from CBS asked secretary of state John Kerry. Whether there was anything that can be done to prevent that he responded almost jokingly in a press conference that if aside gave up all of his chemical weapons that there wouldn't be military actions. Military action the Russians then jumped on that seizing on it and brokering a deal with the Americans. Whereby Assad would give up all of his chemical weapons. Nine months and millions of dollars later it was believed. That all of serious chemical weapons were out of the country some really nasty stuff via acts so Aaron mustard gas labs have been destroyed the Obama administration considered this a real victory. So how with the regime now carry out another chemical attack. Firstly maybe they had more chemical weapons that they simply didn't declare and work removed or maybe they kept some. We're able to keep some of the precursor chemicals needed to make a nerve agent likes Aaron. And a scientists and engineers. In Syria who originally made those chemical weapons are still there. With the know how so if you can get your hands on the precursor chemicals. And still have the experts around. Wall up you have a new arsenal. Not just from the regime's perspective here go from a strategic standpoint knowing that information does make its way out knowing that videos get. Sent very easily now across social media and other platforms. When you have conventional weapons to use that they have been using it against their own population why why Kerry at a chemical attack now. It's a great question and this is the main argument by skeptics as well as by people who support the regime. Many are arguing that it's what's called a false flag attack by the rebels. The argument goes that a sot that the Asad regime is winning this war which they are. That they can get the job done with conventional weapons so why would they use those chemical weapons or straw so much attention from the global community. And possibly risk which is now what's being discussed some sort of serious military retaliation well the simple answer to that question is impunity these solders in feels they can get away with it that they're testing the limits of this new trump administration. Critics of trump or poignant it's pointing to comments by secretary of state. Rex Tillerson who indicated just a few days ago that it was not a priority of this new administration to remove a sought from power. So they're gambling here that there won't be some sort of reaction. The other elements is terror this is such a horrific attack. But a lot of people in Syria are gonna see it all terrified people. And perhaps a lead many in the opposition held areas to despair about ever throwing ever overthrowing. President aside especially. If there's now no international reactions so by doing this is solders who has not only terror are terrorizing its opponents but may be thinking that it could speed up. Their downfall. If they scare them and out. So Alex and now with the Russians as we know you know messaging after these kinds of incidents it's almost as important as the incident themselves. The Russians are saying it was actually the Syrian air force right that bombed a rabble supply. A chemical weapons and I know much of the conversation and pointing back to the regime that you've mentioned how hard it is to get information from their so how can we be certain. That it was the aside regime that carry the fat. Well we can't. Really into it withered arts the Russians who are obviously the series' main backers they claimed yesterday morning that it was the rebels. Making chemical weapons and using them across the border in Iraq. And that the Syrian planes were bombing this rebel facility. Chemical weapons experts who have been poring over this video have shot down this theory for a number of reasons or other this reasoning. For a number of reasons. First of all officials. Today in Turkey who have seen the autopsy of the victims are saying that this was this Aaron that's the Sarin nerve agent Sarin is very hard to make. Likely too hard for the rebels to make. Secondly since nerve agents are so unstable they're often stored in two separate chemicals it's a buying area agent. One of those chemicals in the case of Serran is called iso properly which could blow up if a were struck by a Syrian missile from one of those jets. As the Russians are alleging we haven't seen evidence of that. But let's assume that the cern was already pre mixed if it were bombed it would be destroyed and not disperse and a way that would kill so many people on that goes for other nerve agents as well. Yes rebels have been known to use chemical weapons but in this case all signs now point to these having been manufactured. And dropped by the Syrian regime. Alex we've been seeing over the course of our conversation. Some of those. Very disturbing images try to father young father holding the bodies of his dead twain's other parents cradling the bodies of children as he mentioned so many. Who were injured and killed in the attack. Earlier this week president truck yesterday basically said seeing those images. Crossed many red lines for and that's what sort of got him to change his stance so. What's the possibility that America actually takes military action. Yet he said there also changed his thinking on Syria and that's this is really the million dollar question is net. President Obama had his red line which would of course we now know he ignore president trump. Said that he does believe this was carried out by the Asad regime and that the attack as you said crossed many red sorry. Across many lines he didn't say red line across many lines. But he then refused to say whether that would there be any sort of military action what the consequences of crossing those many lines would be in fact when pressed by those White House reporters who tried to pick it. And talk instead about North Korea which is discussing when she's in paying the president. Of China this weekend. Now you can be sure that this is being debated fiercely at the White House and at the Pentagon right now president trump. May want to send a clear strong message early in his term that is not the kind of X action. That is acceptable. But the president has also shown some willingness to work with the Asad regime and their Russian backers saying that they are also fighting ice this. Which president trump has called his biggest priority in Syria. Now there's no doubt that this is a major test for president trump one of its first major foreign policy and military task. But it's very unclear right now what action if any. You may take on the hikes before I let you go you know you have been there on the ground covering this conflict and bearing witness to so. Many of these terrific images we've been seeing it strikes me now in this conflict goes on as long as it has. There's an entire generation of kids there who are just being born into war who only know. This conflict. And we talk so much about the diplomacy in the leadership in the military strategy I'm just curious about. You're take from what you've seen on the ground about the population. That's being affected. Both Housley heartbreaking apps there what we've been covering this for six years both from the regime's side in Damascus and an of the regime held territories. But also going in on on the on the rebel house side. There is now. A huge swath of a population that has never known anything but war you know if you imagine. You know kids were born six years ago there they've only known this work kids who were you know work twelve will likely. Only remember this or they haven't been in school. There either and refugee camps in the surrounding countries. If they're lucky they've gotten to places like like Europe. And United States but many millions more still stock. In. In Syria many of them displaced. You know we talk about the regime held areas we talk about the rebel held areas. But in of the day so many people frankly are just caught in the middle so when you do go from. Into Syria whether it's on the regime's side or on the on the rebel side these days what you're hearing a lot of us we just want this war to end. There's so much fifty senators there's such a sickness there's such a sense of we've suffered so much. We simply want this to end but as we talked about right off the top. This is not just a Syrian war. This is a war that involves more than a dozen other partners and so many of those partners have bottomless pockets. And so many of those partners don't have to suffer the consequences. Of this brutal war day in day out so they have little incentive. To finish it at the end of the day the Syrian regime. It's something of a pawn in the medalists bear controlled. By by their puppeteers and Russia and Iran. You have the the rebel groups that are controlled by. You know their puppeteers and the US and Turkey. Saudi Arabia and others so. At the end of the day. It it is the Syrian people who were apps that are suffering and there's there's very little hope that the country will be able to put itself back together in a way that was in 2011. One this war broke out it is it is deeply damaged is deeply scarred and and it's obsolete tragedy. Alex mark part live for us in London thank you for doing the near impossible explaining that very complicated region. Thank you. I think all of you for joining us to for more on the story and other you can always go to abcnews.com. Specific if you wanna see some of the back story. To some of the images you are seeing right there on exactly soon for now I'm on an Abbas.

This transcript has been automatically generated and may not be 100% accurate.