The Caspian’s rule against outsiders was never switched on

For most of the past three decades the Caspian was the quiet sea of the former Soviet south. In 2026 it became a place where wars are fought from outside. Israeli aircraft struck an Iranian naval base on its shore in March, and a Ukrainian strike hit an Iranian vessel on it in July. The littoral states answer with a principle they agreed eight years ago: that only their own armed forces belong on the Caspian. That principle has never entered into force, and even if Iran now ratifies it, it will not stop the kind of attack the sea has actually seen.

What has happened on the water

On 18 March Israeli jets hit Iranian naval port and base facilities at Bandar Anzali, which housed missile ships and guard boats, according to RFE/RL. It was the first time the war that began on 28 February had reached the Caspian. The Kremlin spokesman, Dmitry Peskov, said Russia would view any spillover of the conflict into the Caspian "extremely negatively". Moscow's interest is concrete. The sea carries a growing share of Russia–Iran trade, and one Russian trade promoter told RFE/RL that Caspian cargo between the two could double in 2026 to 10 million tonnes.

The second incident came from a different war. On 25 July a strike on an Iranian vessel killed one sailor and injured another. Ukraine said it had targeted Russian warships and vessels carrying Iranian-linked military cargo, and its foreign minister, Andrii Sybiha, urged Tehran to end "any support for Russia's war". Iran called the attack aggression and demanded restitution. After a call between the two ministers, Iran's foreign minister, Abbas Araghchi, said Kyiv had described the strike as "unintentional" and that Iran did not seek escalation either.

What the 2018 convention says

The Convention on the Legal Status of the Caspian Sea, signed in Aktau on 12 August 2018, lists its military rules as principles in Article 3. The parties commit to a "stable balance of armaments" and to military capabilities "within the limits of reasonable sufficiency". They commit to the "non-presence in the Caspian Sea of armed forces not belonging to the Parties", and to not lending their territory to other states "to commit aggression and undertake other military actions against any Party".

Under Article 22 the convention enters into force only when the fifth instrument of ratification reaches Kazakhstan as depositary. Russia, Kazakhstan, Azerbaijan and Turkmenistan have ratified. Iran has not, so none of this is yet binding on anyone.

Why Tehran has changed its mind

After seven years of inaction, Iran's government sent the convention to parliament at the start of August with priority status. The foreign ministry spokesman, Esmaeil Baghaei, noted that the other four coastal states had already ratified and that the treaty needs all five. The government presented ratification as a way to set a clear legal framework among neighbours and to stop outside powers exploiting the region. Araghchi and his deputy, Kazem Gharibabadi, briefed the cabinet on military developments during the discussion, Borna News reported.

The cost to Iran is in the seabed. Article 8 leaves the division of the seabed to agreements between neighbours. Iran International notes that Tehran has long argued for a 20 per cent share for each state, while the modified median line used by the others would give it roughly 11 to 13 per cent. Iranian critics quoted there warn that ratification would weaken Tehran's legal leverage and ease the way for a Trans-Caspian pipeline. That Tehran is prepared to pay this price suggests it now values a legal barrier to outside forces more than a maximal seabed claim it has not been able to settle with its neighbours.

What the rule would and would not cover

The clause is narrower than its supporters imply. Its text addresses the presence of outside armed forces in the sea and the use of a littoral state's territory for aggression. Neither of this year's attacks fits either description. Israel's aircraft attacked a port on Iranian soil rather than deploying forces on the water, and Ukraine's strike was a single attack on shipping, not a standing presence. Neither Israel nor Ukraine is a party, and the convention's principles govern what the parties themselves do. A ratified convention would give the five states a shared legal position to cite. It would not give them a means of stopping aircraft or drones that never enter the sea.

It may also raise questions among the littoral states themselves. Azerbaijan's Power of Unity 2026 exercise with Türkiye and Uzbekistan, which opened in late September, includes a phase at the Boyuk Zira training area in the Azerbaijani sector of the Caspian, with naval and aviation assets, according to AZERTAC. Neither Türkiye nor Uzbekistan borders the sea. The convention does not define what counts as "presence", and joint training on a littoral state's own territory is the kind of case on which the five could differ once the text binds them.

The littoral states' own capacity

A rule that reserves security to the five assumes the five can provide it. On 24 September, 14 Kazakh servicemen died when they were swept into the sea from a boat during the Khazar Qorgany 2026 exercise in Mangystau, The Times of Central Asia reported. President Kassym-Jomart Tokayev replaced the defence minister three days later, five commanders were detained, and officials were given ten days to draw up a reform plan. Critics noted that the boat normally carries eight people, while 19 were reportedly aboard. The accident was not a hostile act, but it shows how thin some littoral navies remain.

Outside powers are also arriving in forms the clause does not address. In New York on 23 September the US government hosted an event on investing in the Trans-Caspian trade route and the TRIPP route through southern Armenia, which also presented its Trans-Caspian Enterprise Fund. Armenia's foreign minister, Ararat Mirzoyan, and Azerbaijan's, Jeyhun Bayramov, both spoke, Public Radio of Armenia reported. Washington's presence on the Caspian is commercial rather than military, and nothing in the convention touches it.

What to watch

The first test is the Majlis vote, and whether Iran attaches reservations on the seabed that its neighbours would have to accept or reject. The second is whether Russia and Iran try to turn the Article 3 principles into a binding protocol with verification, which would need the agreement of Baku, Astana and Ashgabat; Baku, for one, has just trained with Turkish forces on the sea. The third is the war itself. If the US–Iran talks on Hormuz fail, the Caspian's importance to Iran as a supply route will grow, and so will the incentive for others to strike it. A convention that enters force in those conditions would record the five states' preference for a closed sea. It would not, on its own, make that sea safe.

Sources

• President of Russia — Convention on the Legal Status of the Caspian Sea (text), 12 August 2018
• RFE/RL (via GlobalSecurity.org) — With Israeli strike on a Caspian port, Iran war could endanger Russia's trade route with Tehran, 1 April 2026
• Al Jazeera — Kyiv warns Iran against escalation after Ukraine’s Caspian Sea attack, 28 July 2026
• Public Radio of Armenia — Mirzoyan highlights TRIPP’s role in regional connectivity at New York event, 24 September 2026
• Iran International — Iran moves to ratify Caspian Sea pact with seabed rights still unsettled, 7 August 2026
• Borna News — Iran submits Caspian Sea convention to parliament for ratification, 1 August 2026
• The Times of Central Asia — Kazakhstan orders military overhaul after 14 die in Caspian drills, September 2026
• AZERTAC (via GlobalSecurity.org) — Azerbaijan to host "Power of Unity - 2026" joint military exercise, 18 September 2026