When Moscow deployed one of its advanced S-400 Surface-to-Air (SAM) system to Syria following the shoot down of a Russian Su-24 strike aircraft by a Turkish F-16 in late November 2015, both Russian and Western media sources were quick to note that the system is capable of engaging targets at ranges of up to 400km (250 mile) thanks to a new long-range missile known as the 40N6.

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Similar assertions were made following subsequent deployments of S-400 systems to Kaliningrad and Crimea. Much of the confusion on whether the 40N6 has been fielded with the S-400 system has to do with another advanced Russian SAM system – known as the S-300V4 – which Russian troops began receiving in late 2014.

In March 2015, the Russian Defense Ministry announced that a new unspecified 400km range missile intended for use with the S-300V4 had entered service with Russia’s military, leading a number of Russian media sources to assume that the missile in question is the 40N6. …