Covert discussions between Russia and Iran over the development of supersonic cruise missiles continued into the summer, according to newly disclosed correspondence, travel records and patent analysis reported by the Financial Times and British media outlets.

The multi-year project, codenamed C430L, began in 2023 and has enlisted some of Moscow's most experienced missile specialists to supply Tehran with advanced military technology throughout the war involving Iran.

At the centre of the collaboration is a ramjet propulsion system — an engine with no moving parts that allows missiles to maintain flight at several times the speed of sound. By flying at high speeds while staying at low altitudes, these weapons significantly cut the time air defence systems have to detect and intercept incoming strikes.

Defence analysts say the technology is almost certainly intended for anti-ship and land-attack cruise missiles. Fabian Hinz, a senior analyst with Conflict Armament Research, told the Financial Times that the transfer involves strategically sensitive technology Iran has sought for decades, adding that a programme on this scale would have required political clearance from the very top in Moscow.

The leaked files show that state arms exporter Rosoboronexport has coordinated the project alongside NPO Mashinostroyenia, a Russian defence manufacturer placed under United States sanctions in 2014. Travel logs indicate that Russian arms officials and senior engineers made repeated visits to Iran before the C430L contract was formalised.

The technical collaboration has included direct Russian evaluation of Iranian trials. Russian engineers analysed data from an Iranian test of a ramjet propulsion system and questioned Tehran regarding its performance in 2025. In April 2025, Rosoboronexport also offered to dispatch two dozen missile specialists to Iran for consultations.

The missile project fits into a wider deepening of ties between Moscow and Tehran. In June, Russian insiders disclosed that the Kremlin shared intelligence to help the Islamic Revolutionary Guard Corps target American military positions in the Middle East, following earlier talks regarding drone transfers.

The alliance was reinforced publicly on Tuesday when Vladimir Putin met Iranian President Masoud Pezeshkian. Praising the Iranian people's "courage and resilience", the Russian leader told Pezeshkian: "During this difficult time, we are trying to provide you with the assistance you need."

Regional tensions linked to the partnership continue to mount elsewhere. In July, Ukrainian President Volodymyr Zelensky ordered strikes on an Iranian vessel in the Caspian Sea, while Germany directly blamed Russia for an explosive drone incident at Leipzig/Halle Airport in August.

What remains unconfirmed is whether any Russian-assisted supersonic cruise missile has yet been deployed in combat. While Iranian forces have built and tested the propulsion hardware, there is no evidence confirming an operational weapon has entered active service.

I will continue tracking how Western governments respond to these leaked transfers and whether further details emerge regarding Moscow's technical supplies to Tehran. Check back for updates.