the rebels are led by the islamist group hayat tahrir al—sham, or hts.to al-qaeda, but cut ties from the group years ago. hts is listed as a terrorist organisation by the us and others. it controls most of the north—western province of idlib, the last remaining opposition stronghold after more than a decade of civil war. that war began in 2011, triggered by popular protests against assad's rule. russia intervened in 2015, turning the tide against the advancing rebels. the battle for aleppo in 2016 was a crucial point. syrian and russian forces gained control after a gruelling siege. the war has mostly gone quiet since, with occasional eruptions, the last major one in 2020 when syria and its russian allies attacked idlib. now again russian warplanes are bombing aleppo, backing government forces trying to drive the rebels out. the kremlin is assad's most important ally, but it's now also fighting a war in ukraine. iran and the lebanese hezbollah are also sending fighters to syria, but they have been weakened by israeli attacks in the region. that is one re

the rebels, led by the islamist hayat tahrir al—sham, or hts group, are reported to have taken controlthe majority of syria's we start in syria, where the country's military has acknowledged that parts of the city of aleppo have fallen to rebels and it's sustained dozens of casualties in large—scale clashes. this was the centre of aleppo in the early hours, after russian and syrian warplanes bombed islamist rebel positions there for the first time in eight years, in support of the syrian government forces. the rebels, led by the islamist hayat tahrir al—sham, or hts group, are reported to have taken control of the majority of syria's second—largest city after launching a surprise offensive four days ago. the syrian military says it's withdrawing from parts of aleppo to regroup ahead of the arrival of reinforcements. aleppo was the scene of one of the bloodiest sieges of syria's civil war, a conflict which first broke out in 2011. so it was expected that government forces and russians to start some sort of defence. and that's what happened overnight with russian airstrikes against rebel

launched intense air strikes on the city and other areas controlled by the islamist group, hts, hayat tahriral—shamd other opposition groups. sources in the syrian military have told reuters that moscow has promised bashar al—assad's forces extra military aid to thwart the attempted takeover, which they say will arrive in the next few days. merlyn thomas and our bbc verify team have been tracking the situation. at bbc verify, we've been tracking the advance of rebel forces towards the city of aleppo in northern syria by looking at footage posted on social media. this is a video we verified which shows military vehicles moving along a road. it was shared by a media outlet affiliated with a rebel group which appears to be leading the advance. it was posted on telegram with a caption, "starting to enter the city of aleppo." and we have confirmed the location to be on the western edge of the city. you can see some of the vehicles here. another video we verified appears to show men in military fatigues running through the streets. and we have geo—located these videos to a western suburb of the city of a

launched intense air strikes on the city and other areas controlled by the islamist group, hts, hayat tahriral—shamr opposition groups. sources in the syrian military have told the reuters news agency that the army has closed the main roads in and out of the city, as well as the airport. they've also told the news agency that moscow has promised bashar al—assad's forces extra military aid to thwart the attempted takeover, which they say will arrive in the next few days. we can go to dr ibrahim al—assil, senior fellow at the middle east institute. what do you make of what we're seeing in aleppo? thank you for having me. it is a major develop and in the geopolitical scene in syria and the region. the attack itself was expected, there was a buildup for not only weeks and months but almost for about two years. but the rapid collapse of the regime forces around aleppo and now in the city of aleppo and now in the city of aleppo was not only a surprise, it was a shock for many, probably including (unknown term) because it is easy to take control of cities and to govern and now it might find itself with a

launched intense airstrikes on the city and other areas controlled by the islamist group, hts — hayat tahriram — and other opposition groups. sources in the syrian military have told the reuters news agency that the army has closed the main roads in and out of the city as well as the airport. they've also told the news agency that moscow has promised bashar al—assad's forces extra military aid to thwart the attempted takeover which they say will arrive in the next few days. earlier, a seniorfellow at the middle east institute, dr ibrahim al—assil, told me it was a major development. it is an earthquake of what is happening in the geopolitical scene in syria and the region. of course the attack itself was expected. there was a buildup from hts for not only weeks and months for years. but the rapid collapse of the regime forces around aleppo and now in the city of aleppo was not only a surprise it was a shock for many including hts them self because it is easier to take control of cities over governing those cities and now hts may find itself in front of a huge challenge. if hts may find itsel

the rebels, led by the islamist hayat tahrir al—sham, or hts group, are reported to have taken control

the islamist militant group hayat tahrir al—sham and its allies say they have taken control of severalis fighting what it calls a "large scale" attack. more than 180 fighters on both sides have been killed, according to a uk—based monitoring group. it said at least 19 civilians were killed by syrian and russian air strikes in opposition—held areas. more than half a million people have been killed in syria's civil war, which erupted after the government cracked down on peaceful pro—democracy protests in 2011. around the world and across the uk, this is bbc news. it's the first new treatment for asthma attacks in 50 years and researchers at king's college london are describing it as a "game—changer". 0ur health correspondent sophie hutchinson has been looking at the research. the results, published in the lancet respiratory medicinejournal, found a failure rate of 74% when taking the current treatment of steroids, but that dropped to 45% with the new therapy. benralizumab, significantly reducing hospital admission and fatalities. so how does it work? if somebody gets a flare up of their

called — the one that's really swept across and is now dominant in this part of syria — is called hayat tahrirsummarise them, but fundamentally, they were an islamist rebel group. they were explicitly allied some years ago to al-qaeda inside syria. they were proscribed as a terrorist organisation by a number of countries, including the united states. what's happened since then is quite complicated, but basically they've split with al-qaeda. many experts say they have become fundamentally more pragmatic and moderate. for instance, they have been cracking down on al-qaeda and islamic state cells. so they are still islamist in their ideology, but they're not salafi jihadi and sort of as extreme as they once were. and if you look indeed, in the last day or so, they've been reaching out to some christian communities in this part of syria to say, you know, "we understand you might be afraid, we're not here for extremist vengeance or anything like that. " but there is still a debate about whether they've really ideologically made that transformation in a serious way. could assad be toppled and what w

in the arab world, where all of a sudden, out of seemingly nowhere, you have a group like this hayat tahrir al-sham, that is actually going in and moving very quickly. they're advancing at an incredible rate. and if they do actually reach hamas as as ben wedeman has mentioned, they may have already reached the outskirts. according to some reports that could spell a real challenge for the assad regime, could potentially result in its toppling. but we'll see what happens in the next juncture here. >> yeah, and we know that russia's foreign minister has already made calls to several counterparts in the region. ambassador taylor i'm hoping you can help us kind of understand all the dynamics at play here. >> well, the dynamics are that the russians are now overstretched as as ben reported. the russians back in 2015 sent a lot of airstrikes they're doing a little bit more today. but since then they've invaded ukraine and that and they've got their hands full. they got their hands full with the ukrainians. the ukrainians have been fighting now for 1011 days, and the and the russians are stretched

. >> and what we've seen is that over the last three days, these rebel forces led by hayat tahrir al-sham, which is a group, a rebel group, earlier affiliated with al qaeda it has managed to take almost 70 villages west of aleppo city and what we saw is starting this morning they started to enter the western sector of aleppo syria's second largest city and by as the evening progressed, what we saw is increasingly more and more videos of rebel forces getting to the very center of the city. we saw one video of rebel fighters in saadallah al-jabiri square, which is a main very large, open square in the more modern part of the city. and later we saw live streaming video of rebels buying coffee and noodles next to aleppo's iconic ancient citadel. now what this has been is really the result of it appears for one thing, the rebels have clearly been working very hard to prepare for some sort of surprise military offensive. but on the regime's side, it appears that the absence of hezbollah fighters who came from lebanon to syria during the civil war to bolster the weak and often corrupt and incomp

that's hayat tahrir al-sham, one of one of the groups part of this mosaic that has attacked aleppo. that group formally linked to al qaeda. beth, if you would, could you please break down the web of players, the different groups that we're seeing here and their respective goals right? >> i mean this is syria is one of those places that is just so complicated that, you know, anyone looking at this just wants to throw up their hands and say, like, i'm out. >> you know, this is too hard. >> but it is, as andrew was saying, this place where all these different factors come together and in fact, like the syrian people are the least important sadly, in this entire endeavor you have russia that that saved assad from collapse and iran. so these are the the forces backing up assad and keeping him in power. then you have turkey that has shares. the northern border of syria and this is where kurdish forces are. and turkey has wanted to come in and they occupy a little bit of that north, and they've wanted to expand that zone. and then you have the united states also present in the north east o