Iran Turns to Russia via the Caspian to Bypass US Blockade, but Northern Ports Cannot Replace Southern Gateways

US naval blockade constricts trade routes along Iran's southern coast
Iran turns to the Caspian Sea for Russian grain and military supplies
Attacks by wartime adversaries and limited capacity constrain the northern alternative

Iran is turning its attention to a northern transport route that connects it to Russia across the Caspian Sea. With a US naval blockade effectively cutting off trade through its southern ports, Iran is using the Caspian, where direct US Navy control is difficult, to bring in Russian grain and military supplies. Yet the northern ports lag far behind their southern counterparts in cargo-handling capacity, vessel size and rail connections, making it unlikely that the Caspian can fully replace Iran's existing trade network.

Pressure Mounts on Iran's Transport Network

On September 28, the shipping publication The Maritime Executive reported that US naval controls were achieving a near-total blockade of Iran's major southern ports. Since April, the United States has been ordering ships heading to or departing from Iranian ports on the Persian Gulf and Gulf of Oman, including Bandar Abbas, to change course. Vessels that refuse have faced boarding and inspection, as well as forcible disabling by air and naval forces. The measures have severely disrupted the southern coastal transport network, which handled 80% of Iran's total trade before the war, sharply narrowing the country's access to external trade routes. All dates are local.

More recently, the disruption has spread from maritime transport to air cargo. Most international flights to and from Iran have been suspended over the past week, with only some military aircraft and a very small number of flights to Russia, China and other destinations reportedly still operating. The contraction appears to reflect increased US pressure since September 23, including the threat of secondary sanctions against foreign businesses providing refuelling, maintenance and other services to Iranian aircraft. Land crossings are also struggling to handle a surge in freight. According to a September 27 report by Qatar-based Al Jazeera, as many as 1,800 trucks were waiting for days to enter Iran at the Norduz crossing on the Armenian border. Conditions are similar on the route through Türkiye, another critical land corridor. The Associated Press reported that the number of trucks at Gürbulak–Bazargan, the largest land crossing between the two countries, had risen from around 200 under normal conditions to 1,200. Waiting times have increased more than fourfold compared with the period before the war.

The Caspian Emerges as an Alternative Route

Against this backdrop, the Caspian Sea to Iran's north is attracting attention as effectively the country's only remaining route for moving large volumes of cargo. The world's largest inland body of water borders just five countries: Iran, Russia, Azerbaijan, Turkmenistan and Kazakhstan. The Convention on the Legal Status of the Caspian Sea, signed by these states in 2018, prohibits the presence of armed forces from non-littoral states and, in principle, restricts entry and navigation to vessels flying the flags of the five coastal countries. This makes it difficult for the US Navy or other Western forces to seize vessels or blockade shipping routes directly in the Caspian.

Determining exactly what is happening in the Caspian from outside the region is also difficult. Analysis by maritime data platform Lloyd's List Intelligence found that vessels travelling between Russia and Iran repeatedly switch off their automatic identification system (AIS) signals, engaging in what is known as “dark activity”. During these gaps, continuously tracking a vessel's actual location, route and port calls requires separate evidence, such as commercial satellite imagery and port records. There are also concerns that the US security apparatus does not treat the Caspian as a single strategic space. Hudson Institute researcher Luke Coffey has described the region as a “geopolitical black hole” in US policymaking, noting that it is barely mentioned in major American national security and military strategy documents.

Table 1. Strategic Features of the Caspian Sea

Russia–Iran Trade Continues

Russia and Iran have used these geographical and structural advantages to maintain trade across the Caspian since the war began. The clearest example is food. According to Russian grain company ProZerno, Russia supplied Iran with 913,700 tonnes of grain between July 1, the start of the 2026–27 crop year, and September 8. The total comprised 498,100 tonnes of corn, 292,500 tonnes of barley and 123,100 tonnes of wheat. Even in August, when Russia's overall seaborne grain exports contracted, shipments through the Caspian route, primarily destined for Iran, rose 13.4% year on year to 311,700 tonnes.

The Caspian also serves as part of the two countries' military supply network, extending beyond civilian trade. Citing European government documents and Western officials, NBC News reported in August that Russia had supplied Iran with drone components, ammunition and TNT explosives through the Caspian. The documents stated that, by July, more than 20 Russian vessels had crossed the sea to deliver these supplies to Amirabad port in Iran's Mazandaran province. They described the shipments as an effort to replenish Iran's missile- and drone-related stocks depleted by US and Israeli air strikes.

Israeli and Ukrainian Attacks

Parties to the wars have also launched direct attacks in the Caspian region to disrupt military cooperation between Russia and Iran. A prominent example was Israel's air strike on Bandar Anzali in March. Israeli fighter jets attacked the port, on the Caspian coast of Iran's Gilan province, and the Iranian Navy's Fourth Naval District. According to the Israeli military, the targets included naval facilities where dozens of warships were moored, a port command centre, and ship repair and maintenance facilities. Israel said it destroyed four missile boats and a corvette, among other assets. The Wall Street Journal later cited officials as saying that the strike had targeted the Caspian supply route between Russia and Iran.

In July, Ukraine attacked Russian warships and cargo vessels in the Caspian. Ukrainian President Volodymyr Zelenskyy said long-range strikes had hit Russian naval vessels and ships used to transport military supplies linked to Iran. The Security Service of Ukraine (SBU) said the targets included the Russian-flagged general cargo ships Port Olya 2 and Begey. Port Olya 2 is subject to US and Ukrainian sanctions, and Ukraine's Defence Intelligence has identified it as involved in transporting military cargo from Iran to Russia. Begey is also subject to UK and Canadian sanctions. Ukrainian authorities have alleged that it transported ammunition, artillery shells, body armour and helmets from Iran to Russia while its AIS was switched off.

Northern Routes Cannot Fully Replace Southern Ports

Despite the growing attention to the Caspian, experts consider a full replacement of Iran's southern ports effectively impossible. The biggest obstacle is sheer cargo-handling capacity. According to Iran's Ports and Maritime Organization (PMO), the country's ports have a combined nominal capacity of around 300 million tonnes a year, but northern ports such as Anzali, Amirabad and Nowshahr account for only about 10% of that total. PMO head Mohammad Shakibi-Nasab has said that a single large vessel operating at a southern port can carry as much cargo as around 20 Caspian vessels. Even the north's existing capacity is being eroded by falling water levels. United Nations Environment Programme (UNEP) data show that the Caspian's water level has fallen by around two metres since the 1990s and has been declining by more than 20 centimetres a year over the past two to three years.

Connections for moving cargo inland from the ports are also insufficient. Iran is linked to Turkmenistan, Kazakhstan and China through the railway network along the eastern Caspian, but gaps remain in the western rail network towards the South Caucasus. In particular, the roughly 160-kilometre Rasht–Astara railway, a key section of the International North–South Transport Corridor (INSTC) being developed jointly by Russia and Iran, remains unfinished. As a result, much of the cargo moving to and from Russia and Azerbaijan must still travel by road rather than rail. The range of goods that can be transported is also limited. Crude oil, petroleum products and iron ore, major sources of foreign exchange for Iran, require high-volume bulk transport and therefore depend heavily on large southern ports and oil terminals. The main imports currently entering through the northern ports are food and essential goods, including barley, corn, wheat and oilseeds, while exports are concentrated in relatively light products such as processed foods and packaging materials.