But the real story behind the sale--and it's an element I've yet to see discussed very widely--is the way it may reflect a subtle but significant shift in the US posture toward Iran.

It shouldn't surprise anyone to learn the whole deal is actually about Iran. After all, when the US took out Saddam Hussein, it eliminated the Saudis' only other real enemy except al Qaeda (and you can't use fighter planes against jihadis). The Obama administration admitted as much last week; as a senior administration official told the New York Times on Friday, the deal is meant to show the Iranians "that [their] nuclear program is not getting them leverage over their neighbors, that they are not getting an advantage."



What is surprising, however, is that this deal seems to represent a highly controversial shift in how the administration plans to deal with Iran: from what wonks call (borrowing language from the Cold War) rollback to what's known as containment.

In plain language, the difference is between a policy aimed at stopping Iran from getting nukes (rollback) and one aimed at stopping Iran from using them if, or when, it does (containment). A look at the nature of the weapons Washington is planning to sell Riyadh, which reportedly also include the THAAD anti-ballistic missile defense system and an upgrade to the Saudis' Patriot batteries, makes it clear that the package is meant to help one of Iran's largest neighbors (and a longtime target of Iranian provocation) cope with nuclear-armed and potentially more belligerent Persian state.

Now, this may be highly rational; it certainly seems that way to me. Despite Washington's success this spring passing a new round of sanctions against Iran and gumming up Tehran's illicit weapons program through sabotage and other means, the mullahs continue to make slow progress toward a bomb. Ultimately, nothing short of a military strike is going to keep them from getting one (if that; there's in fact a huge debate over whether even a US or Israeli strike could set back Iran's march to nuclear precipice by more than a year or so).

But shifting from rollback to containment, even if it's the more realistic policy and done quietly, is still a dangerous move for the Obama administration, for several reasons. First, making the switch by funneling unprecedented quantities of firepower to the Saudis could fall flat, or even backfire. The kingdom has already been the largest purchaser of US arms for some time now, and despite that fact, has proved utterly incapable of defending itself and its massive oil fields. Second, by upping the quantity of weapons dramatically, the administration risks igniting a regional arms race. (It's worth noting that in 2008, the tiny United Arab Emirates actually spent even more on armaments than the Saudis did.). Apart from its inherent dangers, such a escalatory cycle would pose a major PR problem for a White House that has made global arms reduction a major part of its policy agenda.