Buyan-M-class corvette

The Project 21631 (also known as the Buyan-M) class of corvettes (Small Missile Ships) is an updated variant of the earlier Project 21630 (Buyan) class of small artillery ships. It has a greater displacement, length and beam, with some upgraded sensors and electronic countermeasures. The main difference between the two subclasses, however, is their armament. The Buyan ships are fitted with a BM-21 Grad multiple rocket launcher, hence the name "Artillery ship". The Buyan-M units, however, are equipped with an 8-cell 3S-14 vertical launching system, which is intended to carry the nuclear-capable Kalibr long-range anti-ship/land attack cruise missile,^[6] (and, in theory, the supersonic Oniks and hypersonic Zircon). Differences are also noted in the air defense systems, with the two classes having slightly different SAMs and CIWS.^[7]

Ships of Project 21631 were designated for national economic zones protection, same as the original variants.

A particular advantage for the Buyan-M series were the limitations imposed by the Intermediate-Range Nuclear Forces Treaty (INF) which prohibited land-based medium-range missiles while sea-based ones were not restricted. A river-based corvette could deploy such missiles without being subject to the restrictions.^{[citation needed]}

The ships' small size and displacement enables them to operate within inland river systems, including traversing the Moscow Canal. This allows them to redeploy to various seas around European Russia.

On 7 October 2015, corvettes Grad Sviyazhsk, Uglich, Velikiy Ustyug and Gepard-class frigate Dagestan, deployed in the Caspian Sea, launched 26 Kalibr cruise missiles at 11 targets in Syria. The missiles flew nearly 1,500 kilometres (930 mi) over Iran and Iraq and struck targets in Raqqa and Aleppo provinces (controlled by the Islamic State) as well as in Idlib province (controlled by the al-Qaeda-linked Nusra Front).^[8] According to United States Department of Defense officials, several of these cruise missiles fired from Russian ships crashed in Iran and did not make it to their intended targets in Syria.^[9]

On 20 November 2015, the same warships launched 18 Kalibr cruise missiles from the Caspian Sea at seven targets in Rakka, Idlib and Aleppo provinces.^[10]

In 2016, the corvette Zelenyy Dol was deployed to the Mediterranean Sea, later followed by sister ship Serpukhov.^[11] On 19 August Zelenyy Dol and Serpukhov, deployed in the Mediterranean Sea, launched Kalibr cruise missiles at positions of Al-Nusra terrorist group in Syria. As a result of the strikes, number of terrorist facilities were destroyed, including command post and base near the village of Dar Ta Izzah and weapon production plants and warehouses in Aleppo province.^[12]

On 25 October 2016, Zelenyy Dol and Serpukhov were deployed to the Baltic Sea to join a newly formed division at Kaliningrad.^[6] In 2020, Zelenyy Dol and the Karakurt-class corvette Odintsovo deployed to Arctic waters utilizing Russian internal waterways and illustrating the Russian capacity to transfer light units among the Russian Navy's three western fleets and the Caspian Flotilla as might be required.^[13] A similar deployment was conducted in 2023 by Serpukhov.^[14]

On 28 March 2022, a Buyan-M class corvette fired eight Kalibr missiles from the Black Sea and claimed to have destroyed a Ukrainian arsenal at Orzhev.^[15][16]

On 17 June 2022, a photo emerged of Velikiy Ustyug being towed on the Volga River in a damaged state after a Ukrainian attack.^[17]

On 8 April 2024, Ukrainian military intelligence released a video in which they claimed to have started a fire onboard Serpukhov. The fire reportedly occurred on 7 April. Serpukhov was in harbour at Baltiysk, Kaliningrad Oblast. Ukrainian military intelligence claimed that the fire destroyed "its communication and automation systems."^[18] On 3 July 2024, HUR revealed details of Operation "Rybalka" ("Fisherman"), which involved a former Russian sailor setting fire to the Buyan-class corvette Serpukhov on 8 April 2024. He also stole data "about the Baltic Fleet and the Russian military industry." The former sailor joined the Freedom of Russia Legion after defecting. HUR estimated Serpukhov will be out of action for six months. The ship was targeted for its ability to fire Kalibr and Onyx missiles.^[19]

Published Russian naval documents showed that on 7 August 2025 the Vyshniy Volochyok of the 41st brigade was damaged from colliding with the civilian tanker Nazan in Temryuk Bay while maneuvering to evade attacking Ukrainian drones.^[20]

On October 4, 2025, the Grad was reported to have been damaged, after being struck by Ukraine, on Lake Onega.^[21]

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  Grad Sviyazhsk with decorative lighting in a sunset
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  Uglich
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  Zelenyy Dol
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  Orekhovo-Zuyevo
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  Naro-Fominsk
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  Velikiy Ustug
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  Serpukhov
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  Vyshniy Volochyok
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  Ignushetiya