• SS-21 missiles on their wheeled launchers.

SS-21 missiles on their wheeled launchers. (Photo : Russian Army)

Russia has delivered its largest ever consignment of short-range tactical ballistic missiles to its ally Syria, leaving western observers pondering the reasons why.

Western reports reveal a shipment of 50 OTR-21 Tochka (NATO reporting name: SS-21 Scarab) short-range ballistic missiles arrived at Syria's Mediterranean Sea port of Tartus on Feb. 7. Apart from this shipment being the largest yet between both countries, it's also the largest for this type of missile.

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The Syrian Arab Army currently has an inventory of some 100 SS-21s, which are fired from a six-wheeled 9P129 launch vehicle. The army operates about 12 of these vehicles.

There are three missile models, Scarab A, B and C, and it unclear which of these models was delivered this week to Syria. Whatever the model, the missile can be used for precision strikes on tactical targets such as command posts, troop concentrations and airfields. It can launch a fragmentation warhead to a distance ranging from 70 km to 185 km.

The SS-21 entered service with the Soviet Union in 1976, and is currently in use by 10 countries, including Syria.

What puzzles western analysts about this latest and largest shipment is why it was sent.

One unnamed U.S. official was quoted as commenting that "For someone (Syria) winding down a war, that's a big missile shipment."

Russia's announcement in December 2016 it was reducing its military presence in Syria might have prompted Moscow to deliver the SS-21s, although some western analysts point to evidence Russia is simply rotating units and not reducing its combat strength in Syria.

The Syrian Army has been stingy in its use of the SS-21 and Scud-B tactical ballistic missile against anti-Assad rebels during the Syrian Civil War that began on March 15, 2011.

On the other hand, Russia has been more lavish in using the missile, and only last week fired two SS-21s at anti-Assad rebels in Idlib province.