Russia wants to expand its transit networks – and its influence – south to Iran, but doing so will not be easy. For the Russians, no geographic barrier has ever proved as daunting as the Caucasus Mountains, and few of the Caucasus transit states could be considered Russia's friends. These factors will make it difficult for Russia to build infrastructure that transits the region uninterrupted, but in the end, Moscow and Tehran will likely work together to try to overcome the significant obstacles in the Caucasus and to curb the presence of other major powers in the region.
So far, Russia has managed to build two roads through the South Caucasus to Iran. The first runs along the Caspian Sea, through Dagestan and Azerbaijan, while the second follows the Georgian Military Road through the Jvari Pass in the Caucasus Mountains. However, the first road's use is limited by the historically unfriendly relationship between Azerbaijan and Iran. The second is often closed during the winter and cannot be used easily by the larger trucks that would be necessary in any expansion of overland trade between Russia and Iran or Armenia.
Because of these issues, Russia has actively sought more reliable connections to Iran over the past few years. One solution was to lay down railway lines that extend southward from Russia, down both sides of the Caspian Sea. In late 2014, the Russian railway system was connected to Iran's in this way, with links that passed through Kazakhstan and Turkmenistan. Meanwhile, Iran is still building the Kazvin-Rasht line on its Caspian shore, directly connecting to the Iranian city of Astara on Azerbaijan's border. When complete, the line will link Iran's northern railway branch to the rail network in Azerbaijan and onward to Russia. Still, like Russia's roads, neither railway is a foolproof solution: Both Azerbaijan and Turkmenistan refuse to allow Russia to transport military equipment through their territories, which limits Moscow's uses for the lines.
With transit states hindering Russia's use of road and rail, Moscow has begun to widen its search for alternative routes. One possibility is a road leading from the North Caucasus to the Georgian breakaway territory of South Ossetia before connecting with the important East-West highway, which links Azerbaijan to Georgia's Black Sea ports. Another would be to build 160 kilometers (about 100 miles) of railway between Alagir, in the North Caucasus, to Gori, in Georgia. Each of these options would enable Russia to reach the railway system of every South Caucasus country using the shortest and quickest routes available. The final possibility is a railway through Abkhazia, another Georgian breakaway territory. In October 2015, Russian forces finished reconstructing part of the rail line, which now extends to the territory's demarcation line with the rest of Georgia. Abkhazian officials have hailed the event as a precursor to the railway's full restoration, but given Moscow's support for Georgia's breakaway territories, it is highly unlikely that Tbilisi will ever agree to allow Russia to follow through with this plan.
But neither Moscow nor Tehran has backed down because of this opposition. As completed and ongoing projects in Abkhazia, South Ossetia and Azerbaijan show, both Iran and Russia appear willing to work together to try to find partial solutions to the problem of securing reliable transit in the Caucasus while keeping other foreign competitors out.