Here's What You Need To Remember: The S-400 registers a significant improvement over its S-300 predecessor on several performance fronts. Whereas the S-300 was explicitly designed as a long-range air defense system, the S-400 is currently compatible with four missiles that are meant to satisfy a wide spectrum of operational categories: very long-range 40N6E (400 km), long-range 48N6 (250 km), medium-range 9M96e2 (120 km) and short-range 9m96e (40 km).

From India to Turkey, Russia’s S-400 “Triumf” air defense system is carving an export swathe through the global arms market. Over a decade after its introduction, the S-400 has become one of Russia’s most demanded high-end combat systems.

Even so, Triumf has no shortage of uses closer to the Russian homefront. Earlier this month, Russia’s Baltic Fleet announced that another S-400 battalion has been stationed in Kaliningrad: "The new S-400 Triumf air defense missile system has arrived at its permanent base in the Kaliningrad Region from the Kapustin Yar practice range in the Astrakhan Region after its initial live-fire tests were conducted successfully," their press release read.

Russian news outlet RT reported that the local anti-aircraft regiment received the S-400 with a military parade, part of which can be seen near the end of this video clip. The video also features footage from a recent S-400 drill in Kaliningrad, as well as close-up shots of Triumf systems being deployed.

Commander of the first anti-missile battalion Vitaly Semerenko welcomed the Triumf delivery, noting that there previously "used to be a S-300 anti-aircraft missile system at this position, which is a bit older and had fewer opportunities in terms of target shelling in the area."

Nonetheless, this is not the first S-400 to be stationed in Russia’s heavily armed, central European enclave of Kaliningrad. The S-400’s first known Kaliningrad deployment stretched back to 2012, though it made little news waves at the time. Triumf’s subsequent cameo came in 2016, alongside the Russia’s new Iskander short-range ballistic missile system. That move, described by Russian politicians as a direct response to the expansion of the U.S. missile shield into Eastern Europe, generated much greater western alarm because it occurred in the post-2014 climate of rapid NATO-Russia military escalation in the Baltic region.

The S-400 registers a significant improvement over its S-300 predecessor on several performance fronts. Whereas the S-300 was explicitly designed as a long-range air defense system, the S-400 is currently compatible with four missiles that are meant to satisfy a wide spectrum of operational categories: very long-range 40N6E (400 km), long-range 48N6 (250 km), medium-range 9M96e2 (120 km) and short-range 9m96e (40 km). More importantly, the S-400 is better adapted to the nature of modern aerial combat with its anti-ECM (electronic countermeasures) and anti-stealth tools.

But as previously mentioned, Kaliningrad is already hosting several S-400 battalions; why would the Baltic Fleet deploy another one?

First, consider the strategic context: just as the 2016 S-400 transfer was rationalized by the expansion of U.S missile defenses into Romania, the Kremlin is again bolstering their Baltic deterrence forces on the heels of a recent, 4.75 billion dollar Polish Patriot missile system procurement contract.

The move may also yield certain tactical benefits. A recent Swedish report on Russian anti-air capabilities argued that the S-400 can be overwhelmed with a saturated barrage by dozens of medium-range “air-launched precision-guided stand-off weapons” and decoys. Fending off this barrage would exhaust a given S-400’s supply of loaded medium-range missiles and force it to reload, providing enemy aircraft with an offensive window of opportunity. Assuming that the Swedish analysis is accurate (as Charlie Gao points out, it makes some dubious assumptions about S-400’s operating alone and not being able to discern decoys), the problem could be offset by the deployment of additional S-400 batteries. More S-400’s means more loaded missiles and potentially smaller reload windows, thus rendering the saturation strategy more time-consuming and less numerically feasible.

As the fallout from the dissolution of the Intermediate-Range Nuclear Forces Treaty (NF) continues to unfold, the S-400 transfer is the latest round in Russia’s ongoing expansion of the Kaliningrad air defense forces.

Mark Episkopos is a frequent contributor to The National Interest and serves as research assistant at the Center for the National Interest. Mark is also a PhD student in History at American University. This article first appeared last year and is being republished due to reader interest.

Image: Reuters.