There is no fast, easy way to get from Tehran to Damascus. But people and equipment need to make their way quickly into Syria for Iran's intervention there to meet Tehran's goals.

Iran has been actively involved in the Syrian war for years, fighting on the side of President Bashar al-Assad's regime. Along with Russia, it's the Syrian president's most important protecting power.

But with no good way to get war material to Syria by land or sea, Iran has been turning to the air, using a state airline and a private airline for transportation since 2015, according to the magazine "The National Interest."

Tehran has extended the airlift with the help of both the state airline and a private one.

"It is almost inconceivable that these flights have carried exclusively civilian passengers and innocent cargo," wrote Paul Bucala from the Critical Threats Project at the American Enterprise Institute think-tank. "The increase in the number of Iran Air flights to Syria coincides with increased fighting and more aggressive deployment of Iranian forces. That cannot be happenstance."

Servant of two masters

If there is a second round of Syria talks - initiated by Iran and Russia - in the Kazakh capital of Astana, the representatives of Assad's government will be perfectly aware that they are the guests of their two most important backers in this war, to whom the Syrian regime owes its political survival. There's every indication that without the support of Russia and Iran, Assad would have stepped down - or been forced out - long ago.

On Tuesday, the White House announced that the US would send a representative to the talks in Astana. The announcement came shortly after the US administration said President Donald Trump had held a "very good" call with President Vladimir Putin and they had discussed "Syria safe zones." Trump and Putin may meet on the sidelines of the Group of 20 summit in Hamburg in July, according to the Kremlin. 

It is likely that Iran and Russia will only be able to protect the Syrian president by working together. Either one on its own would not be strong enough. Assad basically has no choice other than to go along with the wishes of his two partners. If he didn't, they would make him well aware of who really holds power in Syria.

"Russia, Iran, and the Assad regime cannot recapture Salafi-jihadi safe havens and secure them over the long-term, given their severe manpower shortages and shortfalls in command-and-control," according to an analysis by the American Institute for the Study of War, published in March. Their military role is, therefore, limited; however, that does not alter the situation that "Assad is not sovereign. Iran and Russia have both inserted themselves deep into the framework of the state."

Complex power relationships

Military power relationships on the side of the Assad regime are correspondingly complex and difficult. According to estimates by the Institute for the Study of War (ISW), after six years of war, the Syrian army has shrunk from 100,000 to 30,000 to 40,000 operational soldiers. However, this group apparently also includes other forces, such as Iranian Republican Guards, as well as various special forces and Syrian volunteer organizations. Hezbollah and Shiite volunteer groups from Iraq and Afghanistan have also lent support to Assad.

Many of the regular Syrian army units have been disbanded; in some places they have been replaced by paramilitary organizations, and some of these are connected to criminal networks. However, according to the ISW, this collapse of the regular structures combined with the spread of guerrilla warfare also helps ensure the survival of the regime.

The ISW said these groups are participating partly for financial reasons while some have been recruited via religious training centers specially set up by Iran. It added that they are controlled by Iranian-led military operations centers in Latakia and Daraa.

Syrians as spectators in Astana

These militant groups are also important because Russia has refrained from deploying ground troops in Syria. In order to avoid losses of its own, Moscow has primarily deployed its air force. The ISW said that while airstrikes do help Iran, it also leaves Iran to provide basic support on the ground.

For the Assad regime, the aid coming from his two protectors signifies both his political survival and his political weakness. During the first round of peace talks in Astana in January, Assad's delegates were more like observers than serious diplomatic negotiators. There's little indication that this will be any different second time round. Officially, Assad is still in power in Syria. De facto, others took over long ago.