The rapid unraveling of the US-Russia relationship over their failed effort to establish a cessation of hostilities between Syria’s government forces and moderate opposition groups may become increasingly dangerous for Syrians and the Middle East as a whole. Indeed, respected Russian defense and foreign policy expert Dmitri Trenin, a former Russian military officer who directs the Carnegie Moscow Center, has argued that Syria could become a “battlefield between the two” and that this is an “exceptionally disturbing prospect that should keep people in Moscow and Washington awake at night.” Trenin is right to be concerned.

The day after the United States issued a press statement announcing its suspension of talks with Russia on implementing the cessation of hostilities, The Washington Post reported on a National Security Council meeting to discuss possible strikes on Syria’s military, including options such as cruise missile attacks on runways, presumably intended to slow or stop Syrian airstrikes (particularly around Aleppo). The next day, Russia’s Defense Ministry spokesman appeared to respond directly to this article. In a press briefing, he warned the United States that Russia had deployed S-300 and S-400 missile systems at its facilities in Syria, that US strikes would threaten Russian military personnel “on the ground” in the country and that Russian air defense crews would “hardly” have time to assess incoming attacks to determine their flight paths. This amounts to a statement that Moscow might respond directly to any US attacks on Syrian forces. In an interview with Al-Monitor, Trenin confirmed this and noted that the spokesman’s reference to “unidentified flying objects” was especially significant. “I take this as a warning that not only US cruise missiles but also its aircraft might become Russian targets,” he said, adding that “Moscow seeks to deter the US from attacking Syrian government forces and assets.”

Also striking is how swiftly the breakdown in the cessation of hostilities has metastasized. Within 72 hours of the US suspension of the Syria agreement, Russian President Vladimir Putin ordered Russia’s withdrawal from a US-Russian agreement to reprocess excess plutonium so that it could no longer be used in nuclear weapons and from two other nuclear cooperation agreements. At the same time, Russia conducted a massive civil defense exercise that the news agency Interfax reported with a photo of emergency workers appearing to practice nuclear decontamination. By the end of the week, US intelligence officials confirmed a media report that Moscow had deployed short-range, nuclear-capable Iskander-M missiles to Kaliningrad, an isolated Russian enclave between Poland and Lithuania. A Russian Defense Ministry official also suggested that Moscow was pursuing reopening military bases in Cuba and Vietnam.

In a presidential executive order, Putin justified his decision on the plutonium agreement by referring to “unfriendly actions by the United States of America in relations with the Russian Federation” before expressing any other concerns. Foreign Minister Sergey Lavrov went further, stating that “our decision is a signal to Washington that it cannot use the language of force, sanctions and ultimatums with Russia while continuing to selectively cooperate with our country only when it benefits the US.”