Recent months have shown sharp differences that have begun to surface between apparently erstwhile allies Russia and Iran, who worked closely in their joint campaign to prop up the regime of Syrian dictator Bashar Al-Assad.
While it is undeniable that the strong cooperation and coordination between the former Kremlin superpower looking to make a comeback and its former Iranian colony has yielded excellent results for the Assad regime, there are still conflicting priorities for the two allies.
Foreign bases on Iranian soil
The problems first began to surface when Moscow made a public relations gaffe that turned into an Iranian political scandal by announcing that Russian warplanes were being launched from Hamadan Airbase in Iran's western provinces.
The Russian defence ministry announced in August last year that its air force had launched sorties, including long-range Su-34 and Tu-22M3 bombers, to strike alleged Daesh targets in Syria from Hamadan. Russia in fact bombed eastern districts of Aleppo that were held by factions from the Syrian opposition at the time, excluding Daesh.
Moscow's public announcement was met by outrage in Iran, as it appeared that it had a secret deal with Tehran to allow the use of its military bases to conduct military operations in the region.
Iranians have mixed feelings towards Russia, acknowledging its assistance in major Iranian policy objectives such as Syria, whilst remaining wary of the fact that Russia repeatedly invaded and occupied Iranian territory throughout the 19th and 20th centuries, even annexing parts of its land.
Iranian state-backed media IRNA carried a statement by national security chief Ali Shamkhani confirming the Russian claim, who also attempted to frame it in a positive light of "strategic cooperation in the fight against terrorism in Syria."
However, in an open session of the Iranian parliament on 17 August, lawmaker Heshmatollah Falahatpisheh drew the legislature's attention to Article 146 of the Iranian Constitution that stipulates that no foreign military bases can be established on Iranian soil.
According to Al-Monitor, Falahatpisheh also said that Russia has a "turbulent foreign policy" and its own "strategic and foreign policy considerations" that may be divergent from Iran's national interest.
Aleppo used as bargaining chip
Although Kurdish news website Rudaw reported the Iranian defence minister, General Hossein Dehghan, as saying that Russia can station its forces at Hamadan "for as long as they need", the Iranian government was soon forced to backtrack.
Days after Falahatpisheh's remarks and Iranian public outcry at a permanent foreign military presence in the Shia theocratic republic by a former colonial power, Iran's Tasnim news agency reported the Iranian foreign ministry declaring that Russia had halted using Hamadan Airbase, and that Tehran would not transfer control of the airbase to Moscow.
Not only was this to relieve pressure on the Iranian leadership after the public embarrassment inflicted upon them perhaps inadvertently by the Kremlin, but it was also the first major indication that the two allies did not have fully convergent views on how the Syrian crisis should be resolved, beyond agreement that the Assad regime must stay.
Following the tripartite Russian-Iranian-Syrian assault on the northern city of Aleppo in November and December last year, a ceasefire and evacuation agreement was reached with members of the Syrian opposition to leave the former major trade hub after the Assad regime and its allies began dragging women and children out of their homes and massacring them.
While Russia was keen for the evacuation of opposition fighters and civilians from Aleppo to Idlib to take place as swiftly as possible, Iran had other designs. Reports soon emerged of Iran-controlled Shia jihadist proxies preventing civilians from leaving the battered city.
According to senior figures in the Syrian opposition, Iran was to blame for the stalled evacuation of Aleppo. The Ahrar Al-Sham anti-Assad faction accused Tehran of taking advantage of the dire humanitarian situation in Aleppo in order to force opposition concessions on two villages dominated by Alawites, a subdivision of the Shia creed that Iran adheres to.
Divergent aims in Syria talks?
Feeling that it had not achieved all it wanted in the Syrian war thus far, Iran then balked at the nationwide ceasefire imposed by Russia and Turkey that began on 30 December.
In association with the Assad regime, Iranian-backed operations against the strategic Wadi Barada valley near Damascus increased in intensity throughout January. Not only was the Ain Al-Fijah spring that supplies the majority of Damascus' four million people with water bombed repeatedly by the regime, but Hezbollah actively shelled and launched assaults against villages in the valley.
With these actions threatening to upend the Russian-backed ceasefire, Moscow despatched a delegation of four officers to assess regime and Shia jihadist violations of the truce following pleas by elders in Wadi Barada. These Russian officers were prevented from accessing the area by none other than the Iran-backed Lebanese Hezbollah.
The assault on Wadi Barada continued unabated, and in the run-up to the recently concluded peace talks in the Kazakh capital of Astana that began on 23 January, the Iranian regime attempted to again challenge Russia for supremacy on the question of post-conflict Syria.
Almost a week before the Astana conference began, Iranian Foreign Minister Mohammad Javad Zarif said that his country was opposed to any US presence at the talks. "We have not invited them, and we are against their presence."
Russia responded soon after with Kremlin spokesman Dmitry Peskov confirming to the BBC that his country would welcome US participation in peace talks, and saying that "Iranians are not welcoming [US participation]. So it is a very complicated issue for a very careful play."
Following the Astana talks, it remains to be seen where the two nations' interests converge and where they diverge. The recent Russian proposal on a new Syrian constitution, however, appears to be designed to appease Iranian interests in Syria, by decentralising rule away from Damascus and into provincial authorities with a greatly weakened president, stripping the Arab identity from the Ba'athist republic.
With the news that Iran is expanding its economic empire in Syria, it is unclear whether Russia, who also has commercial and economic interests in the war-torn state, will challenge Iranian control further, or if they will divide Syria's spoils amongst themselves, with a pliable Al-Assad at least nominally controlling Damascus.