So why did the United States make this move, and why is it potentially dangerous? Here’s what you need to know.
Where did OST come from?
OST was the brainchild of two Republican presidents. President Dwight D. Eisenhower’s 1955 Open Skies proposal was designed to pierce the veil of secrecy surrounding Soviet military programs during the Cold War. Moscow’s anticipated rejection of Eisenhower’s offer reinforced Washington’s claims that the U.S.S.R. was insincere about disarmament.
President George H.W. Bush reprised the idea just before the fall of the Iron Curtain. In the post-Cold War context, OST as signed in 1992 was designed to support the new era of confidence and cooperation between East and West.
Arms control gives countries information about each other. That’s both good and bad.
The controversy over OST illustrates a fundamental dilemma in arms control. New research by Andrew J. Coe and Jane Vaynman shows that countries face a “trade-off between transparency and security” when they enter into such agreements.
The problem is that countries must disclose information to comply with an arms-control agreement — but compliance means they may also reveal other security information that aids their adversaries. Too much information may allow other countries to exploit it for offensive purposes; too little, and effective verification of compliance with an agreement is impossible. As Vaynman noted here at the Monkey Cage in 2017, this problem affects U.S. demands that Iran disclose more information than it previously agreed to under the 2015 nuclear deal.
The United States has now accused Russia of undermining this balance by denying the United States and its allies the full benefits of OST transparency, while exploiting OST data for offensive ends. However, most arms-control experts and many former policymakers believe that the costs of leaving the treaty outweigh the risks of remaining.
What are the benefits of the Open Skies treaty?
OST’s benefits may not be immediately obvious because the treaty does not significantly improve the United States’ ability to collect intelligence on its own. The sensors allowed on flights are probably inferior to those aboard U.S. reconnaissance satellites, for instance. But Washington can’t always share such highly classified intelligence with allies, most of which lack comparable capabilities and rely more heavily on OST. Nor would it be likely to divulge such intelligence to Russia, especially during a dispute between the two countries.
So OST plays an important role by providing a common pool of verified information. All OST parties have access to the certified data collected from every surveillance flight. That benefits U.S. allies that don’t possess their own intelligence collection capabilities — but this data also creates an accepted set of baseline facts to support U.S. diplomacy with both allies and adversaries. For example, in 2018, Defense Secretary Jim Mattis revealed that OST “imagery was a key visual aid during U.S. engagement with allies and Russia regarding the  military crisis in Ukraine.”
Yes, Russia has acted to diminish OST transparency
In 2014, Moscow imposed an unpermitted 500-kilometer limit on flights over the strategically important enclave of Kaliningrad. Since 2010, Russia has denied flights near Abkhazia and South Ossetia, two breakaway regions of Georgia. Russia also denied a U.S.-Canadian flight over its “Tsentr” military exercise in September 2019.
However, the United States was addressing these issues within the treaty — with some signs that the situation was slowly improving. Washington declared Russia in violation of OST in 2017 and restricted Russian access to Hawaii and Alaska in retaliation.
This February, Moscow authorized a U.S.-Estonian-Lithuanian mission over Kaliningrad that was above the 500-kilometer limit. Although James Gilmore, U.S. ambassador to the Organization for Security and Cooperation in Europe, remained dissatisfied with Moscow’s compliance in early March, he noted some progress, including a Russian pledge not to deny exercise overflights in the future.
The U.S. withdrawal announcement also alleges that Russia has used OST to improve offensive targeting against the United States and Europe, contravening the confidence-building spirit of the treaty. Without further information from the Trump administration, it’s difficult to assess the nature and seriousness of this allegation. In 2016, Vice Adm. Terry Benedict, director of Navy’s Strategic Systems Programs at the time, described any potential gain in this area as “of only incremental value in addition to Russia’s other means of intelligence gathering.”
Will the U.S. move put arms control at risk?
There may be collateral costs of OST withdrawal; the treaty itself may survive without U.S. participation, but Washington’s exit will diminish the agreement’s value to Russia significantly. Moscow’s withdrawal would probably kill OST, ending a key source of intelligence for many NATO allies. This unilateral U.S. move, taken over its allies’ objections, is likely to damage NATO cohesion.
The Trump administration’s decision on OST adds further pessimism regarding the future of New START, the last remaining major U.S.-Russia arms-control agreement. New START, which limits the two countries’ strategic offensive nuclear forces, will expire in February 2021 unless the White House decides to extend it.
In deciding to withdraw from OST, the Trump administration appears to have miscalculated the balance between transparency and security, even as other European signatories affirm the benefits of the treaty. In this context, analysts aren’t confident that President Trump will weigh risks and benefits adequately the next time around.
James J. Cameron is a research associate in the Department of War Studies at King’s College London and an affiliate with the Oslo Nuclear Project at the University of Oslo. He is the author of “The Double Game: The Demise of America’s First Missile Defense System and the Rise of Strategic Arms Limitation” (Oxford University Press, 2017). Follow @cameronjjj.