Russia and Iran: an uneasy alliance
Vladimir Putin's visit to Tehran this week has been greeted with much enthusiasm in official circles.
There has been warm praise for his decision to head straight from the airport to a meeting with Iran's Supreme leader, Ayatollah Khamenei.
And the encounter apparently went so well that Iran's veteran former foreign minister Ali Akbar Velayati was moved to describe it as "the best and the most important in the whole history of the Islamic Republic".
Although few details have emerged of what was said between the two, the Iranian media has widely quoted a comment attributed to Mr Putin, assuring the Ayatollah that "Unlike some others, we never stab our allies in the back".
It is clear that for Tehran, getting Moscow on side for the campaign in Syria has been a big foreign policy coup.
It was also a huge relief after a difficult summer in which it was becoming increasingly clear that Iran and its allies Hezbollah and the Syrian army were struggling to support Bashar Assad on the ground.
With the death toll of Iranian revolutionary guards forces rising weekly, President Putin's decision to bring Russia into the conflict was clearly good news for Iran and has helped for now to stabilise the Syrian regime.
Social media criticism
But not all Iranians are convinced an alliance with Russia is a good idea and President Putin's visit has prompted many to take to social media this week to remind their compatriots of some of the less successful moments of recent Iranian-Russian cooperation.
"That lousy nuclear plant you've been building for us in the last 20 years, was meant to be operational ten years ago, it's not even half finished," said one user, raising the thorny issue of the much-delayed Russian-built Bushehr nuclear plant.
You never even once voted against the Security Council Resolutions which have made our lives like hell in the last ten years," said another. "Name three good things that Russian has ever done to Iran"
Behind this scepticism is a difficult shared history between between Iran and Russia stretching back centuries.
For most Iranians, the Russians are the dangerous and unpredictable enemy in north: the people with whom they have fought big battles and suffered bitter defeat.
The Treaty of Turkmenchay in 1828, which set the borders between the Persian and Russian empires, and forced the Persians to concede large swathes of territory to Russia, is still a bye-word in the Persian language for a unfair settlement or contract.
Marriage of convenience
Many question whether a marriage of convenience between two states with such a history of adversity can last, but for now it is clear that Russia and Iran's leaders see their new alliance as their best chance to maintain influence in Syria and in the region as a whole.
And it comes at a time when tensions between Iran and Saudi Arabia show no sign of abating.
President Hassan Rouhani's pledge to reach out to Saudi Arabia and improve relations has so far failed to achieve results and neither has it attracted much popular support.
Increasing numbers of Iranians now see the Saudis as "the enemy" - the country that supports so-called Islamic State (IS) and is therefore a direct threat to Iran.
The Treaty of Turkmenchay:
Agreement between Persia (modern day Iran) and the Russian Empire, which concluded the Russo-Persian War (1826-28).
Signed on 10 February 1828 in Torkamanchay, Iran.
Persia ceded to Russia control of several areas in the South Caucasus: the Erivan Khanate, the Nakhchivan Khanate, and the remainder of the Talysh Khanate.
The boundary between Russian and Persia was set at the Aras River.
These territories now make up parts of modern-day Armenia, Azerbaijan and Turkey.
Such is the animosity that many ordinary Iranians used to criticizing the Revolutionary Guards force as oppressors at home are now hailing them as heroes risking their lives to defend Iran and the Middle East from the extremism of IS.
Viewed from this perspective the Russians have come to the aid of Iran just at the right time to help it in its lonely fight against the extremists moving ever closer to its borders.
And the fact that Moscow's intervention has resulted in some military success on the ground in Syria, means the new alliance is paying dividends.
Possible fault lines
But many possible fault-lines could open up in Russia's relationship with Iran in the coming months.
One issue could be the future of President Assad.
Iran has made it clear that President Assad must stay on, and his future is non-negotiable.
In Tehran this week both Mr Putin and Ayatollah Khamenei reiterated support for Bashar Assad, but elsewhere Moscow has hinted there may at some stage be more room for manoeuvre.
President Putin came to Iran promising big plans for cooperation and investment in a wide range spheres from oil and gas to construction, power generation and railways.
Hopes are high but with both states now experiencing an economic downturn, how much of this becomes a reality remains a question.
And in Russia some analysts are already warning that in moving closer to Iran, and with it Hezbollah and the Syrian regime, Moscow must be careful not to alienate Sunni countries and risk losing influence in the wider Middle East.
There is a saying in Persian to describe hell: it is a place with scorpions so horrible and venomous that you would find no choice but to find shelter with serpents.
Beyond the smiles in Tehran this week it's a saying Iran and Russia might have cause to remember as their Syrian joint venture unfolds.