Could Russian S-400s Protect Syria Against Cruise Missiles?

On the eve of last week’s Western air strikes on Syria, Russia warned that it would shoot down any Western assets attacking Syria; the Russian defence ministry even claimed that its Pacific fleet jets had conducted exercises to ‘intercept and destroy a low-flying long-range cruise missile’.  

But the US, British and French strikes came and went, and no Russian response materialised. Nonetheless, with at least the option of further Western air strikes still open, a couple of questions arise: with its assets in the Middle East, is Russia able to respond?; and do the Russian forces in Syria, and particularly the S-400 surface-to-air missile (SAM) batteries at Khmeimim air base and Masyaf missile base and the S-300VM batteries at Tarsus Naval base, have a real capability to hit Western warships?

Both are air/tactical ballistic missile defence systems, so attacking land-based or naval targets is a secondary task so SAMs are little threat to US Navy carriers or destroyers. The effective land-attack range for those SAMs is also limited to the radar-horizon (roughly 30–40 km, or slightly longer if deployed on hills, as in Masyaf). Therefore, it is highly unlikely that Western naval targets would be within strike range during any further engagements.

The Russian-supplied Bastion coastal defence missile systems operated by the Syrians are a threat; they would be able to attack surface combatants within a range of roughly 300–350 km if provided with external targeting information, such as from Russian planes patrolling the Syrian coast. But the Bastion’s strike range is limited to around 120 km if required to attack in sea-skimming mode, which would certainly be the case for targets protected by Aegis air/missile defence system, as US naval formations are. Nor could they reach Cyprus.

Except in the case of an extremely lucky hit, it would most likely take two–three hits by Bastion missiles to put an Arliegh Burke-class destroyer or Ticonderoga-class cruiser out of action in combat circumstances, and up to eight to twelve Bastion missiles to put an aircraft carrier out of operation.

Syrian government forces have no more than four to six launchers with two missiles per launcher, so they lack the capacity to seriously attack US naval platforms in the Eastern Mediterranean.

The Russian forces’ ability to protect Syrian sites against Western missiles is another matter. The S-400 system is designed to engage aircraft (predominantly fixed-wing ones) and cruise missiles at a range up to 250 km with its 48N6series SAMs. Their main shortcoming is that the S-400s land-based combat engagement radar can’t see targets itself at that range unless they are flying at altitudes above 30-40,000 feet

The effective engagement range of the Syria-deployed Russian air defence systems against cruise missiles (flight altitude around 30–100 m) or low-flying aircraft is limited to their radar horizon, which for such low-flying targets is approximately 30-40 km. That means that Russian systems deployed in northwest Syria cannot protect targets further than 40 km or so from their positions at Khmeimim and Masyaf, as well as Tartus naval base.

That said, both the S-400 and S-300VM are effective within their limited potential intercept range against cruise missiles. To increase effectiveness of intercepting low-flying cruise missiles, S-400 SAMs were designed to pop-up high upon launch and then execute a ‘look down - shoot down’ engagement detecting fast-moving targets against background surface by their Doppler frequency shift of the illuminating S-400 combat engagement radar’s return signal.

In the case of a massive cruise missile attack, the S-400 system would most probably employ the ‘shoot-assess-shoot’ tactics, firing one SAM against each detected cruise missile, rather than pair against every incoming target to increase probability of kill.

This approach is viable because, on detection, cruise missiles are comparatively easy targets since they can’t both detect an incoming SAM and undertake evasive manoeuvre/deploy decoys to avoid being intercepted, as a crew of any manned aircraft under attack could.

It is possible then to say that, as a rule, every ten S-400s launched would intercept between four and six incoming cruise missiles within the effective engagement zone of approximately 30-­40 km radius centred on the combat radar’s location.

There are two substantial operational restrictions, however, which mean that the Russian air defence ‘bubble’, while impressive, is far from invincible. First, the 92N6 combat engagement radar of the S-400s operates within a limited directional sector of 90–120 degrees within which it detects incoming threats and illuminates them for SAMs to lock on their targets.

The semi-active seekers of the S-400s 48N6 family of SAMs require an external radar to permanently illuminate the targets assigned to them for intercept. That means that the engagement radar must keep illuminating targets throughout the launch and intercept sequence and is unable to train in different directions. This makes the S-400 susceptible to defeat by so-called ‘star attack’ tactics: multiple missiles approaching a single objective simultaneously from widely dispersed different directions.

Every S-400 battalion consists of one or two acquisition radars, the 92N6, and up to four ‘fire’ batteries, with one ‘leader’ and two ‘subordinate’ launcher vehicles each. Russia deployed two S-400 units to Syria: one complement provides air defence of Khmeimim, while the other is deployed to a base (co-located with Bastion bunkers) 13 km northwest of Masyaf in the Hama Governorate.

So, in case of any massive cruise missile attack, the Syria-based Russian S-400s would struggle, if tasked to break down the attack, to deal with missiles coming from the Mediterranean and the Gulf (in almost opposite directions) simultaneously, as they did last Saturday. The same is true for any S-300 systems.

The second restriction on Russia’s intercept capabilities is the limited size of SAM magazines available for S-400 batteries. Every S-400 launcher (of which four are in Khmeimim and four in Masyaf) carries four SAMs ready for launch. That makes just 32 SAMs available for engagement of incoming cruise missiles.

After all this complement of interceptors is expended – which will happen after engaging a maximum of 32 cruise missiles shooting down between twelve and nineteen of them – the S400s would need reloading.

The standard time required for that operation according to Russian military regulations is 50 minutes. Highly trained crews could potentially reduce that to 25–30 minutes. However, even such a spectacular performance would leave a wide window when S-400 would be unable to execute its air defence role. All the co-located Pantsir-S1 point-defence systems can do is to protect S-400s against direct strikes, itself a major job.

Russia has many other capabilities that can threaten the US, and plenty of capabilities that could be prepositioned on Syria’s soil. All that can be said at this stage is that the existing Russian air defence systems there cannot protect the country against sustained Western military actions.

The views expressed in this Commentary are the author’s, and do not necessarily reflect those of RUSI or any other institution.