It had appeared to be a conflict frozen in time, but the operation launched with blistering speed by Syrian opposition fighters has turned all of that upside down.
It is also a potent reminder of the complexity of the Syrian conflict.
What was a stalemate has revealed that the regime of President Bashar al Assad may very well be standing on clay feet.
Whether the rebel push continues its momentum and transforms into a wider offensive remains to be seen – but its significance politically and militarily is immense.
Aleppo was once the country’s largest city and was a key battleground in the civil war – it has also been a stronghold for the regime.
What’s happening now is a major blow to the government as it shows how fragile its grip on power has become.
It also demonstrates that the rebels have the determination and the military capability to challenge regime authority in key strategic areas.
The rebels comprise many different groups who’ve fought against the regime since the start of the Syrian uprising.
Among them, the biggest is Hayat Tahrir al Sham, which controls most of the north-western territory held by the opposition.
The group was linked to the terrorist group al Qaeda but has renounced those ties.
Much of the video that’s emerging is reminiscent of the violent uprising against the Assad dictatorship in 2011 – descending into a bloodbath from the so-called ‘Arab Spring’.
Officially, the offensive was launched as a way of stopping regime air strikes on opposition-held territory.
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It may be that the rebels themselves are surprised by the lack of government resistance and how successful they’ve been in the space of three short days.
The Syrian government has portrayed what’s happening as a “large-scale terrorist attack” and has vowed to reverse the losses.
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There are of course wider questions as to why this is happening now?
President Assad would most likely have lost the war had he not been bailed out by the Russian air force and the Iranian Revolutionary Guard, as well as a tapestry of militant groups – including Hezbollah.
Russia is struggling for resource in Ukraine and has diverted its air force from the Syrian theatre.
Iran and its proxies have been battered by Israel after they tried to exploit the carnage of the 7 October Hamas attack on Israel.
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With these forces not as strong as they were, there’s been a chink in the regime’s armour and the rebels it would seem have seen their chance and not let the opportunity escape.
The question now is whether the opposition fighters will be able to remain on the front foot and consolidate their position and perhaps even launch further attacks on centres of power.
At the moment, the situation remains highly volatile and uncertain.
The advance certainly challenges the established order, but it is still far from clear whether this is a setback for the regime, or the start of a major phase of escalation.
