WASHINGTON: That rumble under your feet you sensed this morning was the earthquake caused by the decision of one of America’s closest allies, Saudis Arabia, to join Turkey in buying Russia’s vaunted S-400 surface to air missile system.

The announcement carried extra diplomatic weight as Saudi King Salman was visiting Russia when the Saudis made the announcement.

Former NATO and European Command leader, retired Adm. James Stavridis, called the sale “a step backwards in US foreign and defense policy.” Since World War II, when President Roosevelt agreed with King Faisal that we would guarantee Saudi sovereignty in return for access to their oil, the kingdom has been one of our closest allies, notwithstanding the 911 attacks led by Saudi citizens.

“While the enormous global arms market is a free trade zone, it is disconcerting to see close US Allies like Turkey and Saudi Arabia buying significant systems like the S-400 air defense from Russia,” Stavridis, now the dean of the Fletcher School of law and Diplomacy, writes in an email. “It decreases interoperability, opens up cyber vulnerabilities, exposes additional real intelligence to Russia, and reduces the tendency of the US to truly open its technology transfer process to partners.”

While Stavridis, long known as a warrior-diplomat, does not say it explicitly, his comment about tech transfer is seminal. Should Saudi Arabia proceed with this sale, it may lead to the United States deciding not to sell advanced command and control systems or aircraft to them. Why? Fear that the Russians could get access to highly classified data about our systems’ vulnerabilities.

One of America’s top experts on arms sales was surprised by the Saudi’s announcement, as he suspects was the US government. “This is especially surprising given Trump’s announcement during his Saudi visit that his administration approved a very large package of defense systems for Saudi Arabia. That suggests USG officials knew nothing about the Saudi S-400 decision,” writes Frank Cevasco, former longtime head of international affairs at the Pentagon and a veteran consultant to American and foreign companies on arms sales.

The impact of this sale will reverberate well beyond the simple purchase of the S-400, Cevasco says. Military operations and intelligence may be affected. “The US has a large number of personnel, communications systems, military aircraft, ships, and vehicles in the region.

“The Saudi’s will not be able to link the S-400 with Saudi’s current (US and Europe-sourced) infrastructure, nor will they be able to connect the S-400 with US systems. More troubling to me is that Russia will gain a foothold in a nation that for decades has depended largely on defense systems acquired from the US and Europe,” he writes. “That alone ensured a measure of interoperability among US, European and Saudi forces. That interoperability will remain in most areas, but not in the air and missile defense realms. While I don’t have any first hand insight, I worry that the Russian system may contain a capability to collect electronic signals from US and allied emissions.”

Turkey also upset the Western allies by choosing the S-400 over US or European systems. Cevasco, who wasn’t involved in either the sale to Turkey or Saudi Arabia, says he suspects Turkey’s decision to select the S-400 was driven in part by Turkey’s wish to signal to the US and NATO that “it will do what it perceives as its best interests.” He also bets that Russia “offered a very inviting price (driven by a desire to capture a place in a NATO member nation), and offered technology transfer and industrial participation of a magnitude the US would never consider.”

And, in a comment that will be read with glum faces by many In the US defense industry, Cevasco says the Saudis may have acted because of the long and difficult history of their experience buying advanced weapons over the last 30 years. Most sales, he notes, “were achieved only after much hand-wringing by Washington’s political community and Executive Branch staffs.” With his usual deft touch, Cevasco wryly notes that he suspects “decisions come substantially faster in Moscow than in Washington.”

A former senior official of a major NATO ally characterized the purchase as “quite surprising in terms of strategic balance.” The source noted the irony that “the Saudis are angry with the US since the Iran agreement (Joint Comprehensive Plan of Action), while the Russians are clear supporters of Iran…”

And it certainly raises interesting questions about the purported $110 billion arms sales President Donald Trump announced during his recent visit to the oil-rich kingdom. Given how much of that sale is, to say the least, fuzzy, the S-400 decision also raises questions about how committed the Saudis are to much of the future US arms sales.