Syrian opposition forces began preparations to seize Aleppo a year ago but the assault was delayed by war in Gaza and ultimately launched last week when a ceasefire took hold in Lebanon, the head of Syria's main opposition abroad told Reuters.
The insurgents were able to seize the city and other areas so quickly in part because Hezbollah and other Iran-backed fighters who support Syria's president were still distracted by their conflict with Israel, Hadi al-Bahra said on Monday.
The Turkish military, which is allied with some of the insurgents and has bases across its southern border in Syria, had heard of the armed groups' plans but made clear it would play no direct role, he added in the first public comments on the rebel preparations by an opposition figure.
The assault in northwestern Syria was launched last Wednesday, the day that Israel and Lebanese armed group Hezbollah began a truce ending more than a year of fighting.
"A year ago they (the rebels) started really training and mobilizing and taking it more seriously," said Bahra, president of the National Coalition of Syrian Revolution and Opposition Forces, the internationally-recognised Syrian opposition.
"But the war on Gaza ... then the war in Lebanon delayed it. They felt it wouldn't look good having the war in Lebanon at the same time they were fighting in Syria," he said in an interview in his Istanbul office.
"So the moment there was a ceasefire in Lebanon, they found that opportunity ... to start."
Rebel commanders have separately said they feared if they had started their assault earlier, it might have looked like they were helping Israel, who was also battling Hezbollah.
The rebel operation is the boldest advance and biggest challenge to Syrian President Bashar al-Assad in years in a civil war where front lines had largely been frozen since 2020.
Syrian and allied Russian forces have launched counter attacks, which Bahra said are "destabilising" Aleppo and Idlib.
The opposition retaking of Aleppo also paves the way for Syrians displaced elsewhere in the country and up to 600,000 in Türkiye to eventually return home, Bahra said.
"Due to the Lebanese war and decrease in Hezbollah forces, (Assad's) regime has less support," he said, adding Iranian militias also have fewer resources and Russia is giving less air cover due to its "Ukraine problem".
Asked about any prior Turkish awareness of Syrian rebels' plans, a Turkish official told Reuters "there was no such thing as our country's permission or support".
Hezbollah did not immediately comment on whether its war with Israel opened the door to Syrian rebel advances in Aleppo, where it also had personnel.
Damascus did not immediately comment on whether it risks destabilising the region with air raids.
