Direct proof of use
Direct public evidence places the 2A65 Msta-B in Russian service in Syria during the Syrian Civil War. RUSI's November 2015 assessment of Russian forces in Syria listed six 2A65 Msta-B towed howitzers from the 8th Artillery Regiment and eighteen 2A65 Msta-B howitzers from the 120th Artillery Brigade among the Russian land forces committed to the operation.
The same RUSI assessment reported signs that Russian artillery assets were already providing ad hoc fire support for Syrian army operations near Aleppo, with additional reports of Russian artillery fire near Homs and Hama. Conflict Intelligence Team separately analyzed November 2015 footage from eastern Homs and near Palmyra, identifying 2A65 Msta-B howitzers being fired and noting Russian-language command audio in one clip.
Sources: RUSI Russian Forces in Syria, CITeam New Weapons in Syria
Timeline
The public record is concentrated around Russia's autumn 2015 intervention. CITeam described a late-October 2015 convoy photograph in Latakia governorate as one of the first signs of Msta-B howitzers in Syria, then cited November 7 and November 11 videos showing the guns in use in eastern Homs and near Palmyra. On November 13, RUSI published a force assessment that counted twenty-four Russian Msta-B howitzers in Syria and tied Russian artillery to fire-support activity near Aleppo, Homs, and Hama.
Sources: CITeam New Weapons in Syria, RUSI Russian Forces in Syria
Battlefield role
In the Syrian theater, the 2A65 Msta-B was documented as Russian towed tube artillery rather than a Syrian army inventory item in the cited direct-use evidence. CITeam contrasted Msta-B sightings with D-20 and D-30 howitzers used by Syrian government troops, and in April 2016 noted that Msta-B howitzers had been repeatedly spotted in Syria accompanied or operated by Russian soldiers.
The howitzer's reported role was conventional indirect fire support for pro-government operations. RAND's republication of James T. Quinlivan's War on the Rocks analysis described the Russian artillery battery as better suited than heavy rocket artillery to directly support combat troops with indirect fires in combined-arms operations, and said Russian artillery in Syria signaled support for combined-arms campaigning alongside Syrian forces.
The available sources support deployment and firing by Russian forces in support of the Syrian government and allied side. They do not provide a complete sortie-by-sortie fire log, a public total of rounds fired, or independently verified target details for each Msta-B engagement.
Sources: CITeam Aleppo Howitzer Battery, RAND Artillery Returns, War on the Rocks Artillery Returns