Last week, Carl Levin, chairman of the Senate Armed Services Committee, called for a no-fly zone inside Syria. He had just heard Admiral James Stavridis, the Supreme Allied Commander for Europe, explain that NATO’s Patriot missile batteries deployed in Turkey could shoot down Syrian military aircraft in a radius of twenty miles. Stavridis added that the missiles “would be helpful in breaking the deadlock and bringing down the Assad regime.”

Although Levin had separately called for destroying Syria’s air defenses, he saw Patriots as offering intervention on the cheap: “a way without putting boots on the ground and in a way that would be fairly cautious, that would put additional pressure on Assad and also create a zone where Syrian people who are looking for protection and safety could come without crossing the border and becoming refugees.”

Levin may be technically correct, but he is practically wrong. The background and capability of the the Patriots in Turkey show why the senator is misguided.

In the summer of 2012, after Syria downed a Turkish reconnaissance plane, Ankara shifted to a more aggressive policy, demanding that NATO intervene to topple the Assad regime. The alliance was deeply divided on the issue. Some, like Germany, were outright opposed, and more hawkish allies, like France and Britain, were partial to arming the rebels instead of pursuing a Libya-style campaign.

The deployment of Patriots to Turkey—for the third time in two decades—was a compromise. It was intended to demonstrate alliance solidarity to a country wary of merely verbal commitments. It also provided an insurance policy against the prospect of a collapsing regime firing its ballistic missiles at Turkey, much as Saddam Hussein had done to others in both Gulf Wars.

Patriot missiles are ideal for these two defensive missions. But they have a tightly circumscribed military role, which makes them ill-suited for expansive military intervention. Turkey requested twenty Patriot batteries for complete territorial coverage, but NATO officials deemed this excessive and sent six batteries: two each from Germany and the Netherlands, and an additional two from the United States. The PAC-3 battery can hold up to sixteen missiles, while the PAC-2 can hold up to four. Both of those can engage jets and, depending on their altitude and speed, low-flying helicopters.

Thus, apart from protecting Turkish population centers, the Patriot—and specifically the US batteries deployed to Gaziantep—could bring the airspace above key battlegrounds in the civil war, such as the city of Aleppo, into range. But this is harder than Senator Levin seems to think.

Coverage and Range

The Patriot’s limited range and the number of batteries means that this deployment could only cover small patches of Syrian territory. Assuming a sixty mile range for aircraft, a figure employed by a number of experts, the only battery close enough to the border to engage Syrian targets would be a U.S. Patriot battery in Gaziantep. That would place the still-contested city of Aleppo just within range. Even Al Raqqa, which in early March 2013 became the first city to have fallen to the rebels, is well out of range. German and Dutch batteries have been deployed in Kahramanmaras and Adana, which are both incapable of reaching anything other than insignificant slivers of airspace along the border.

However, if we accept Stavridis’ more conservative estimate for the Patriot’s range against aircraft (this can differ according to the altitude of the target and the intervening terrain), about 20 miles, then that would put even the U.S. batteries completely out of range of Syrian airspace, and even too far away to reach the border town of Kilis.

To be sure, NATO could add more batteries and shift its existing deployments closer to the border. But moving the batteries might compromise coverage of Turkish population centers, something that would be politically problematic. Moreover, European NATO members are unlikely to countenance any such change in the mission, and might even pull their own batteries out of Turkey in such a scenario. The German and Dutch parliaments debated long and hard for the current mission, and agreed to the deployment on condition that, as NATO’s Secretary General put it at the time, “It will in no way support a no-fly zone or any offensive operation.”

Cost and Numbers

Using Patriot in an anti-aircraft role might also be implausibly expensive. A single PAC-3 missile costs between $3 and $4 million, which represents a high proportion of the unit cost of the aircraft it would be targeting. Moreover, the batteries being deployed in Turkey can hold only a limited number of interceptors (between twenty-four and ninety-six, depending on the mixture of interceptor missiles).

Even if one accepts that Turkey may be sent additional, spare interceptors, expending this limited stockpile on Syrian aircraft might leave Turkey vulnerable to ballistic-missile salvos, which would defeat the primary purpose of the Patriot deployment.

Of course, the hope is that a no-fly zone would be a sufficient deterrent to Syrian pilots, such that no missiles would need to be used. As Stavridis told Senator John McCain, “I think that whenever aircraft are shot down, that is a powerful disincentive.”

Friendly Fire

There is a reason why no-fly zones have historically been handled by patrolling aircraft (as over Libya in 2011) rather than ground-based missiles. If, as senators Levin and McCain have demanded, Turkish or Allied aircraft were also tasked with destroying Syrian air defenses at the same time as a zone were imposed, this would create considerable problems with crowded airspace.

During the First Gulf War, for instance, the destruction of the Iraqi air force and absence of cruise-missile threats allowed the coalition to configure Patriot batteries to ignore everything except ballistic missiles. Lower and slower threats could be screened out. By 2003, the rise of Iraqi cruise-missile and UAV threats forced a change in tactics. But that shift came at serious cost in terms of friendly fire. During the 2003 Iraq War, an American Patriot battery downed a British Tornado jet killing its crew; a US Navy F/A-18 was also shot down, and a US F-16 was forced to destroy a ground-based radar that had “painted” the jet (that is, locked on to the jet to target interceptor missiles).

The Patriot system can be configured to only deal with ballistic missiles, which would theoretically make the airspace safer for Turkish and allied aircraft. But not without the unavoidable cost of reducing the threat to Syrian jets. In all likelihood, Patriot will not be configured to screen out other threats, in part because Syria—like Iraq in 2003—possesses Russian-supplied cruise missiles. As such, the Patriot deployment will be accompanied by the establishment of strict air corridors for Turkish jets operating on or close to the border, which limits what they can do.

Advantages

The Patriot does offer some protection against Assad’s ballistic missiles. Beginning in December 2012, the Assad regime has used multiple Scud and Scud-type missiles. It fired around forty in January and February 2013 alone, from a total inventory of seven hundred or so missiles. But Patriot is not a panacea. It does not intercept artillery shells—the only projectiles that have actually crossed the border so far—and the older interceptor missile has well-documented flaws that could limit its effectiveness against a Syrian Scud attack. Some studies found that, during the Gulf War, Patriot's intercept rate was near-zero. Although the new, PAC-3 missile represents a major improvement on its predecessor, it has not been battle-tested against Scuds, only other types of missiles.

Ankara would welcome NATO intervention in Syria, and will be heartened by the noises coming out of the U.S. Congress. But the Patriot deployment is a primarily defensive move. Reorienting it for an offensive mission poses technical and logistical hurdles that make it far harder to implement a no-fly zone than one might glean from the recent exchange between Stavridis, Levin and McCain.

The United States can intervene in a range of other ways, from directly providing arms to unilaterally striking at Syrian military targets from aircraft carriers or air bases in Turkey. But it would be misleading to think that Patriots offer a deus ex machina for a civil war now entering its third year.

Shashank Joshi is a research fellow of the Royal United Services Institute in London, and a Ph.D. candidate at Harvard University's Department of Government. You can follow him on twitter @shashj.

Aaron Stein is a doctoral candidate at King's College, London and a researcher specializing in proliferation in the Middle East at the Istanbul-based Center for Economics and Foreign Policy Studies. He blogs at Turkey Wonk. You can follow him on twitter @aaronstein1.

This article is based on research conducted for a co-authored article in The RUSI Journal, ‘Not Quite ‘Zero Problems: Ankara's Troubles in Syria’, published in March 2013.