Table of Contents

Within the broader U.S.-Russian dispute over missile defense, a particular point of contention is the United States’ European Phased Adaptive Approach (EPAA). This initiative seeks to defend NATO against Iran.1 To this end, the United States has deployed SM-3 Block IB interceptors in Romania. It now plans to deploy more capable SM-3 Block IIA interceptors at the same site and at a second site in Poland. The launchers at each of these Aegis Ashore installations are adapted from the U.S. Navy’s MK-41 Vertical Launching System, which is used on ships equipped with the Aegis air and missile defense system to launch SLCMs and other missiles as well as SM-3 interceptors.

Russia believes that the EPAA may threaten its ability to target the United States with ICBMs. The United States’ November 2020 test of an SM-3 Block IIA interceptor against an ICBM-class target has added to Moscow’s unease.2 The U.S. Department of Defense contends that this interceptor “has the potential” to contribute to the defense of the homeland against “rogue states’” ICBMs, which have less capability to penetrate defenses than Russian ICBMs.3 Moreover, to be useful for homeland defense, SM-3 Block IIA interceptors would need to be deployed near the United States; systems located in Europe would be unable to catch a Russian ICBM. These considerations do not seem to have assured Moscow, however, which may have overestimated the capabilities of the SM-3 interceptor—in particular, its burnout speed (that is, its maximum speed, which is reached immediately after its motors have ceased firing).

Russia’s concerns about the EPAA extend beyond the interception of its ICBMs to the possibility that the launchers could be used to fire offensive missiles, particularly cruise missiles. In response, the U.S. Department of State has indicated that the “Aegis Ashore Missile Defense System” (a term that appears to include more than just the launchers themselves) “lacks the software, fire control hardware, support equipment, and other infrastructure” required for launching offensive missiles.4 It has also stated that “the defensive nature of the Aegis Ashore sites is documented in U.S. basing agreements” with Poland and Romania.5 Russia has made clear that it places little value on these assurances, noting, for example, that the United States has conducted a test launch of a cruise missile from a land-based MK-41 test launcher.6

The United States and its NATO allies have compelling reasons to try to address Russia’s concerns. Most importantly, such concerns could spark inadvertent escalation. Moscow has threatened to attack Aegis Ashore installations preemptively in a crisis or conflict—presumably both to ensure the effectiveness of its nuclear deterrent and to prevent cruise missile attacks that could undermine its ability to wage a conventional war.7 Meanwhile, in peacetime, Russian concerns complicate the development of arms control agreements, including measures to manage the Poseidon torpedo and Burevestnik cruise missile, which Russia is developing to penetrate U.S. missile defenses. Indeed, if Russian concerns about missile defense are not successfully managed, Moscow may take further countermeasures—such as the expansion of its strategic nuclear forces or the development of additional kinds of exotic strategic delivery systems—adding yet more fuel to the incipient arms race.

Solution Concept

Efforts to manage the dispute over Aegis Ashore should focus on the development of a transparency regime to demonstrate that (1) SM-3 interceptors located in Europe cannot threaten Russian ICBMs because they have insufficient burnout speed and (2) European Aegis Ashore installations cannot launch offensive missiles or do not contain missiles other than SM-3 interceptors. Successfully implementing this regime would not resolve the entire missile defense dispute or even address all of Russia’s concerns about the EPAA.8 However, it would ameliorate an acute part of the problem and could also catalyze a process for managing other Russian and U.S. concerns. Washington could indicate that if the transparency regime for Aegis Ashore installations is implemented successfully and if Russia starts to address U.S. concerns on NSNWs—by, for example, agreeing to inspections of empty warhead storage facilities (see chapter 2)—then the United States will be willing to negotiate additional steps to manage the missile defense dispute.

A Transparency Regime for European Aegis Ashore Installations

At the invitation of the United States, Russia should observe one flight test of an SM-3 Block IB interceptor and one of an SM-3 Block IIA interceptor to measure, with Russian equipment, the interceptors’ burnout speeds.

The United States should commit to (1) notifying Russia in advance of the first European deployment of any type of missile defense interceptor with a burnout speed greater than 3 kilometers per second (1.9 miles per second) and (2) inviting Russia to observe, at least sixty days prior to the interceptor’s first deployment in Europe, a flight test to measure, with Russian equipment, the interceptor’s burnout speed.

The United States should commit to refrain from using any denial and deception practices that would interfere with Russian measurements of the interceptor’s speed during any test observed by Russia pursuant to this agreement.

The United States should reaffirm to Russia the exclusively defensive purpose of European Aegis Ashore installations and commit to refrain from (1) loading offensive missiles into European Aegis Ashore launchers and (2) modifying such launchers so they become capable of launching offensive missiles. The United States should further commit to engage in good-faith negotiations with Russia over practical transparency measures, including inspections and/or the use of remote monitoring equipment.

Russia should agree to take equivalent steps if it deploys in Europe any missile defense interceptors with burnout speeds greater than 3 kilometers per second on ground-based launchers derived from naval vertical launching systems.

In 2011, the administration of then U.S. president Barack Obama invited Russia to measure an SM-3 interceptor’s burnout speed—though the proposal appeared to apply to just one flight test.9 Moscow rejected that overture as “propagandistic.”10 The current proposal will hopefully be more attractive because it is more comprehensive. It would apply to each interceptor type that has been or will be deployed in Europe unless its burnout speed is lower than 3 kilometers per second, in which case it could not meaningfully contribute to strategic missile defense operations—as Russia and the United States previously agreed.11 Meanwhile, the confidence-building measures relating to offensive missiles aim to operationalize U.S. commitments already made to Poland and Romania about the exclusively defensive purpose of Aegis Ashore installations.


Interceptor burnout speed. The United States generally conducts interceptor flight tests from the Pacific Missile Range Facility in Hawaii. Russia could use its missile range instrumentation ship, the Marshal Krylov, to measure the interceptor’s burnout speed.12 Given that this ship’s radar likely has a range in excess of 600 kilometers, the vessel could be positioned on the high seas (that is, in international waters) at a site of Russia’s choosing. As such, Russia does not actually need an invitation to monitor U.S. interceptor flight tests—though cooperation would have two advantages. First, the United States would inform Russia of the test in advance, giving it time to position the ship. Second, the United States would commit not to interfere with Russian measurements of the interceptor’s speed.

Exclusively defensive purpose of European Aegis Ashore installations. The first step in developing any verification approach would be meetings between U.S. and Russian officials, including technical experts, so that the United States could identify some or all of the “fire control hardware, support equipment, and other infrastructure” that is missing from European Aegis Ashore installations and thus renders them incapable of launching cruise missiles.13 As part of this process, the United States should provide Russia with commercial satellite imagery and internal and external photographs that highlight differences between Aegis Ashore installations and their sea-based equivalents. The United States could also consider offering Russia a one-off exhibition of the land-based MK-41 test launcher in California—which has been used to launch a cruise missile—and, with the host state’s permission, an Aegis Ashore installation in Europe.

The confidence-building measures relating to offensive missiles aim to operationalize U.S. commitments already made to Poland and Romania about the exclusively defensive purpose of Aegis Ashore installations.

Based on this information, the two sides should then attempt to jointly identify externally observable distinguishing features (EODFs) between the land- and sea-based launchers. The outcome of this exercise would determine the optimal verification approach.

The most straightforward case would arise if the two sides jointly identified EODFs that could be detected with satellite imagery. Verification could then be facilitated by a U.S. commitment not to interfere with Russian NTM—a common feature of many arms control agreements that might be generally helpful in addressing Russian concerns about the EPAA.

A second possibility is that EODFs are identified but are visible only from the ground. In this scenario, periodic on-site inspections, with the host nation’s consent, would be needed so Russian inspectors could verify the absence of one or more components needed to launch cruise missiles.

The third and most challenging case would arise if the United States and Russia were unable to jointly identify any EODFs. The most direct approach to verification would then be for the United States to permit Russian inspectors to periodically select and view the inside of an agreed number of Aegis Ashore launchers to check that they are loaded with missile defense interceptors and not cruise missiles (similar to inspections of the missiles inside ICBM silos or SSBN launch tubes pursuant to New START). To facilitate such inspections, which would again require the host government’s consent, the United States should provide Russia with identifying characteristics for each type of missile defense interceptor deployed in European Aegis Ashore launchers (fortunately, SM-3 interceptors look very different from Tomahawk cruise missiles).

Under any scenario, Russia could use NTM to try to detect the loading of offensive missiles into launchers. It therefore could be helpful for U.S. technical experts to explain to their Russian counterparts how the loading of interceptors and offensive missiles can be distinguished—if indeed they can. Such cooperation would be particularly important if Russia and the United States failed to identify any EODFs and if the United States was unwilling to allow Russian inspectors to view the interceptors inside launchers. In this case, to enhance Russia’s ability to detect any loading of offensive missiles, the United States could (1) permit Russian inspectors to install and use remote monitoring video equipment so Russia could continuously observe specified areas of European Aegis Ashore installations and (2) commit to notifying Russia at least twenty-four hours in advance of the loading or unloading of European Aegis Ashore launchers so it has time to make any necessary preparations for observing the process with NTM.

On-site access of any kind would require Russia and the United States to negotiate a politically binding verification protocol. From a U.S. perspective, a key consideration would be ensuring that Russian inspectors could not learn classified information other than that officially disclosed pursuant to the inspection agreement. To this end, the shrouding of equipment not subject to inspection could be helpful. A separate agreement between the United States and each host nation would also be needed.


Technical feasibility. Designing a regime to verify the exclusively defensive nature of Aegis Ashore installations could prove tricky. The primary challenge would probably be the joint identification of EODFs—an issue that Russia and the United States have frequently disagreed on in other contexts. If the two states failed to agree on EODFs, it might nonetheless be possible for Russia to ascertain that the launchers are configured for defensive purposes by verifying they are loaded with interceptors and not cruise missiles.

Measuring the burnout speed of an interceptor should be straightforward for Russia, which would rely on its own equipment. This speed is probably the single most important parameter for determining the extent of any threat posed by European Aegis Ashore installations to Russian ICBMs—but it is not the only one. As a result, Russia’s gaining confidence in this speed should reduce the scope for disagreement between Moscow and Washington but might not eliminate it entirely. Therefore, this proposal would be best implemented as part of a broader U.S.-Russian dialogue over missile defense, in which the two sides could discuss how to determine whether defenses threaten ICBMs.

Political feasibility. This proposed measure is intended to address Russian concerns and should be paired with one to address U.S. concerns, such as inspections of empty warhead storage facilities (see chapter 2). Even if it is, however, the proposal would stir up controversy within both the United States and NATO. Domestic critics would probably argue, as they did in 2011, that permitting Russia to measure the burnout speed of a U.S. interceptor would disclose classified information that could compromise national security. Yet, as the Obama administration concluded back then, this information would not meaningfully help Russia (or any third party to which Russia disclosed this information) to defeat U.S. defenses. Critically, to protect against Russia’s learning much more sensitive information (such as the performance of the interceptor’s sensors), the United States could continue to use denial and deception techniques (such as the encryption of telemetry data) that did not interfere with Russian speed measurements. Meanwhile, orchestrating Russian inspections on the territory of a U.S. ally would be politically sensitive, but, as history demonstrates, hardly infeasible.

All these difficulties, however, pale compared to the long-standing acrimony between Russia and the United States on missile defense. The two states have long approached this issue with seemingly irreconcilable positions. Moscow has demanded legally binding guarantees without giving any indication that it is willing to offer the United States anything in return. Washington has insisted that it can offer nothing more than politically binding confidence-building measures—that is, when it is prepared to engage at all.

Today, however, there is an opening for progress, albeit a slight one. Russian officials have indicated a new willingness to consider politically binding confidence-building measures. The Biden administration, meanwhile, appears to be more willing than its predecessor to try to address Russian concerns. To improve the prospects for progress, Washington should frame this proposal as the first step in a long-term process to address a wider range of concerns that could potentially include the development of legally binding instruments. In this spirit, this proposal would not be a one-off exercise; it would permit Russia to measure the burnout speed of each interceptor type deployed in Europe and would provide Russia with an ongoing and verified commitment about the exclusively defensive purpose of European Aegis Ashore installations.


1 U.S. Department of Defense, “Missile Defense Review,” 2019, 69,

2 Ministry of Foreign Affairs of the Russian Federation, “Briefing by Foreign Ministry Spokeswoman Maria Zakharova,” Moscow, November 19, 2020,

3 U.S. Department of Defense, “Missile Defense Review,” 55.

4 U.S. Department of State, Bureau of Arms Control, Verification and Compliance, “Refuting Russian Allegations of U.S. Noncompliance With the INF Treaty,” fact sheet, December 8, 2017,

5 Ibid.

6 President of Russia, transcript of “Meeting With Permanent Members of the Security Council,” August 23, 2019, The Kremlin, Moscow,

7 Andrew E. Kramer, “Russian General Makes Threat on Missile-Defense Sites,” New York Times, May 3, 2012,

8 Additionally, Russian officials have expressed concerns that the United States may convert European missile defense interceptors into land-attack ballistic missiles. See U.S. Department of Defense, transcript of “DoD News Briefing With Secretary Gates and Gen. Cartwright From the Pentagon,” September 17, 2009, See chapter 8 for a proposal to help address this issue. Separately, the United States could commit to not testing any type of missile defense interceptor located in Europe against a land-based target.

9 Susan Cornwell and Jim Wolf, “U.S. Invites Russia to Measure Missile-Defense Test,” Reuters, October 18, 2011,

10 “Russia Dismisses U.S. Antimissile Test Proposal as Propaganda,” Nuclear Threat Initiative, November 9, 2011, available at

11 Amy F. Woolf, “Anti-Ballistic Missile Treaty Demarcation and Succession Agreements: Background and Issues,” 98-946F, Congressional Research Service, April 27, 2000, 17,

12 “Upgraded Missile Range Instrumentation Ship to Support Launches at Vostochny Cosmodrome,” TASS, September 16, 2015,

13 U.S. Department of State, Bureau of Arms Control, Verification and Compliance, “Refuting Russian Allegations of U.S. Noncompliance With the INF Treaty.”