The United States recently constructed an Aegis Ashore ballistic missile defense site in Romania, prompting considerable Russian backlash. The Russian government has made a variety of complaints, including that Aegis Ashore blunts Russian strategic deterrent. Other Russian analysts have argued that Aegis Ashore poses an offensive threat. US officials countered, arguing that Aegis Ashore was not a threat to Russia. These competing claims are worthy of examination. First, though, it is important to understand what Aegis Ashore is and how it functions.
What is Aegis Ashore?
Aegis Ashore is a static, ground-based ballistic missile defense system that utilizes the proven Aegis combat system. Aegis is a highly capable air defense system which utilizes the SPY-1D passive electronically scanned array radar and Mk 41 vertical launch missile cells. The Aegis system is usually installed in warships; Ticonderoga-class cruisers and Arleigh Burke-class destroyers, the principle surface combatants of the US Navy, both utilize Aegis. While ships equipped with Aegis often carry a wide variety of missiles, the Aegis Ashore sites are only slated to accommodate SM-3 ballistic missile interceptors. The Aegis Ashore system is capable of intercepting short and medium range ballistic missiles using the SM-3. The SM-3 is optimized for high-altitude performance, meaning it can only intercept exo-atmospheric targets. In other words, any missiles intercepted by the SM-3 must be in outer space. Ballistic missiles which have entered the atmosphere could be dealt with by a shorter-range antimissile system, such as a Patriot battery or an SM-6. The Aegis Ashore sites could theoretically utilize SM-6s, but no plans to this effect have been announced.
Various Russian officials and individuals have objected to the Aegis Ashore site in Romania. One complaint put forth is that the Romanian Aegis site could pose a threat to Russian intercontinental ballistic missiles aimed at the US. This assertion is basically invalid. First of all, current SM-3 interceptors are not designed to intercept ICBMs reliably. Second, even when future upgraded SM-3 interceptors are considered, the geographical position of Aegis Ashore Romania means that it will never pose a threat to Russian ICBMs, since they would pass over Scandinavia and Northern Europe, not Romania.
A more interesting argument put forth by some Russian analysts is that the Aegis Ashore sites could pose an offensive threat. While Aegis is intended as an anti-missile system with no offensive capabilities, its Mk 41 VLS cells are capable of launching Tomahawk cruise missiles. While it is thus wholly possible that Aegis Ashore sites could launch Tomahawks, the threat posed by such a contingency is minimal. The Romanian Aegis Ashore site has a meager 24 launch cells installed, which means it could launch a maximum of 24 Tomahawks. Furthermore, each cell used for a Tomahawk would be one less cell available for an SM-3, and the SM-3 is a much more valuable asset than the Tomahawk, so there is no reason the US would replace SM-3s with Tomahawks. As far as offensive capabilities go, the US already has a massive arsenal of aircraft carriers, cruisers, destroyers, strategic bombers, and strike fighters in or around Europe and Russia. The additional threat posed to Russia by a few Tomahawks at an Aegis Ashore site would be negligible to say the least.
Even though fears of the Aegis Ashore offensive capabilities are overblown, it is interesting to note that Aegis Ashore may actually constitute a treaty breach on the US’s behalf, as a 1987 INF treating banned the US and Russia from producing ground-based cruise missile launchers; Aegis Ashore is certainly a ground-based system capable of launching cruise missiles, even if that may not be its intended purpose.
Of course, the Romanian Aegis site would pose a threat to Russia’s European deterrence, as its coverage is significant. In a regional conflict, Aegis Ashore could pose a threat to any Russian ballistic missiles aimed at Romania or neighboring countries.
But again, Aegis Ashore’s lack of magazine depth mitigates the threat posed. The 24 SM-3 interceptors housed at the Romanian site would be no match for the thousands of short-range ballistic missiles fielded by Russia. This decision to only install 24 launch cells reinforces the US claims that European Aegis sites are aimed at Iran and not intended to dilute Russian deterrence.
The real threats to Russian missile power
While the Romanian Aegis site will probably never pose a threat to Russia, other deployments should have Russian military officers worrying. For one, a Polish Aegis site is planned. Since Poland is farther north, it could possibly pose a threat to Russian ICBMS only if the SM-3 missile is improved significantly so that it can engage ICBMs in boost and midcourse phase. Preliminary indications are that the new SM-3 blocks will probably have some level of anti-ICBM capability, but how effective they are remains to be seen. The Polish site would only pose a major threat if it were to feature a significantly larger number of launch cells than the Romanian one.
Many other aspects of the US ballistic missile defense strategy are being improved, such as the kill vehicles for the Ground-based Midcourse Defense system, the radars of the Patriot, and the command systems which bring various assets into communication. As a whole, these advances pose far more of a threat to Russian deterrence than the Aegis sites.