In March 2016, Mr Putin ordered the "main part" of Russia's forces to withdraw from Syria, saying their mission had "on the whole" been accomplished.
Defence Minister Sergei Shoigu said Russian aircraft had flown more than 9,000 sorties over almost six months, killing more than 2,000 "bandits" and helping Syrian government forces regain control of 10,000 sq km (3,860 sq miles) of territory, including 400 population centres.
The claims have not yet been independently verified, but it is clear the air campaign turned the tide of the war in favour of Mr Assad, allowing Syrian government ground forces to regain territory around Latakia, in the southern province of Deraa and around the divided northern city of Aleppo.
What do critics say?
Moscow stressed that its air strikes only targeted "terrorists", but activists said Russian aircraft mainly bombed Western-backed rebel groups and civilian areas.
In December, Amnesty International said Russian aircraft appeared to have directly attacked civilians by striking residential areas with no evident military target, which it warned might amount to war crimes. Russia's defence ministry dismissed the report as containing "fake information".
However, the UK-based Syrian Observatory for Human Rights reported in early March that 1,733 civilians, including 429 children, had been killed in Russian air strikes, along with some 1,492 rebels and members of the al-Qaeda-affiliated al-Nusra Front, and 1,183 Islamic State (IS) militants.
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