When Syria's president visited Iran late last year, he received a heroes' medal and spoke about unbreakable bonds in a ceremony broadcast on national television.
Now, a nervous leadership in Iran has imposed a media blackout on Bashar Assad's struggle against a swelling Syrian uprising and Tehran faces the unsettling prospect of losing its most stalwart ally in the region.
The Islamic Republic managed to choke off its homegrown "Green Revolution" after the disputed June 2009 presidential election. But now it is being dragged into the uprisings sweeping across the Middle East and stirring unrest in Syria, and unfriendly neighbor Bahrain.
On the deadliest day of the Syrian rebellion Friday — when more than 100 people were killed by authorities — President Barack Obama accused Assad of seeking Iranian help to use "the same brutal tactics" unleashed against demonstrators almost two years ago.
For Iran, its ties with Syria represent far more than just a rare friend in a region dominated by Arab suspicions of Tehran's aims. Syria is Iran's great enabler: a conduit for aid to powerful anti-Israel proxies Hezbollah in Lebanon and Hamas in the Gaza Strip.
Should Assad's regime fall, it could rob Iran of a loyal Arab partner in a region profoundly realigned by uprisings demanding more freedom and democracy.
"Iran and Syria represent the anti-U.S. axis in the region. In that respect, Iran wants to ensure that Syria remains an ally," said Shadi Hamid, director of research at the Brookings Doha Center in Qatar.
Iran may still have other options in the region. It has ties with Iraq's Shiite-led government, growing bonds with Turkey and is making overtures to post-revolutionary Egypt.
But the uprisings also have sharply boosted hostility toward Iran from the wealthy — and increasingly influential — Gulf Arab states that believe Tehran is encouraging Shiite protesters in Bahrain and elsewhere.