ALEPPO - In Aleppo, portraits of Russian President Vladimir Putin hang shoulder-to-shoulder with those of his Syrian counterpart Bashar al-Assad, signalling Moscow's rise at the expense of Damascus's other ally, Iran.
The rivalry between the two primary backers of the Syrian government is becoming increasingly palpable, according to Syrian officials and a Russian analyst.
Iran is proud to have intervened early on in Syria's six-year war, bolstering the Assad regime with men, weapons, and economic aid.
But it was Russia, which entered the conflict with its first air strikes in support of Assad on September 30, 2015, that transformed its trajectory.
"Although both countries support the regime, their strategies on how to defeat the uprising differ," said a Syrian member of parliament, speaking on condition of anonymity.
The primary divergence is over Turkey, a years-long rebel backer with which Syria shares its long northern border.
Moscow has formed an unlikely alliance with Ankara since 2016, envisioning an end to the Syrian conflict as a compromise with Turkey.
But Tehran abhors this approach.
Iran has "differences of views with Turkey with regard to Syria, and they're very serious differences of views, but we have found a common ground," its Foreign Minister Mohammad Javad Zarif recently told Lebanon's Al-Mayadeen television.
Tabnak, a website run by the former chief of Iran's powerful Revolutionary Guards, Mohsen Rezai, presents a less diplomatic view, suggesting in January that "the inclusion of Turkey in efforts to put an end to war in Syria" could pose "a threat" for Iran.
- 'Price we had to pay' -
Those differences truly crystallised in December as Syrian government forces battled to retake Aleppo's devastated opposition-held east.
Iran and allied militias sought total surrender from rebels encircled in the second city, a source close to the regime said in Aleppo.
But, the source added, Russia had already agreed with Turkey on safe passage for east Aleppo's 34,000 residents.
The deal infuriated Iran and its allies in the Shiite Lebanese militia Hezbollah, who tried to spoil the agreement.
As a consolation prize, however, Iran and its allies successfully included the evacuation of Fuaa and Kafraya, two Shiite villages besieged by rebels, in the deal.
"The agreement with Turkey was indispensable for finishing with Aleppo because every time the Syrian army advanced, Ankara allowed hundreds of rebels in," a retired Syrian officer said.
"To avoid yet another failure, Moscow got Ankara to agree to close the border, strangling the rebels. Russia then secured a safe exit for them," the officer said.
"It was certainly difficult for those that were fighting on the ground but it was the price we had to pay to win," he said.
Tensions have only grown since, with Russia and Turkey leaving Iran out of a cessation of hostilities they brokered in late December.
Tehran joined Ankara and Moscow in sponsoring the first talks between regime forces and rebels in January in Kazakhstan.
- 'Interests align' -
After Aleppo's fall, all eyes turned to the largest remaining rebel bastion: Idlib, the northwestern province controlled by an increasingly tense alliance of rebels and jihadists.
Tehran has advocated a blitz assault on Idlib, mainly to break the rebel siege of Fuaa and Kafraya, but Russia has vetoed the idea.
A new front so close to the border and against Ankara-backed rebels would risk direct confrontation with Turkey, a possibility Moscow is unwilling to entertain.
"Russia is wary of Turkey, but it prefers squeezing it and limiting its movement, instead of mounting a full-frontal attack," a political figure in Damascus said.
Turkish forces and allied rebels have indeed been left with little wiggle room in northern Syria. They seized the town of Al-Bab from Islamic State group jihadists in February without a word of protest from Russia.
But now, surrounded by government forces and US-backed groups, they are unable to push further east to fulfil Ankara's goal of leading the battle for IS's stronghold in Raqa.
Much of Iran's strength is drawn from the thousands of militiamen it commands in Syria, which "represent a huge contingent of fighters with which (the Russians) must find a way to cooperate," Russian military analyst Pavel Felguenhauer said.
"Our ties with them are very complicated," he admitted.
But Russia is also increasing its own boots on the ground in Syria, even after scaling back its aircraft there.
"Russia's presence in Syria is rapidly growing. Since the fall, the number (of military personnel) has nearly doubled and will soon be 10,000," Felguenhauer said.
Russia is also cultivating its own proxies on the ground just like Iran, for whom Hezbollah, as well as Shiite fighters from Iraq and Afghanistan, have become indispensable.
"We've created an 'indigenous infantry' which is cheaper than Russian mercenaries," Felguenhauer said, comparing them to US-backed Iraqi tribes that fought Al-Qaeda or Moscow's Chechnyan allies.
Russia has already helped form, finance, or arm two Syrian factions -- the Desert Falcons and the Fifth Legion -- as well as the Palestinian Quds Brigade.
"Russia is a great power with a geostrategic vision that includes Syria, while Iran is a Shiite regional power," the Syrian political figure said.
"Their interests can align, but they are not always identical."