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A Venn diagram of Tamerlan Tsarnaev terror watch lists

If you're confused about the byzantine web of watch lists designed to stop terrorists in their tracks, you're not alone.

Today, the FBI came under greater scrutiny with the revelation that suspected Boston Marathon bomber Tamerlan Tsarnaev was in fact on multiple government watch lists ahead of his deadly massacre in Boston last week. According to Reuters' ace investigative reporter Mark Hosenball, Tamerlan was placed on the government's highly classified Terrorist Identities Datamart Environment (TIDE) database and the declassified Terrorist Screening Database.

What does that mean, and how do these lists compare to more serious lists such as the "No Fly List" or the lethal "Disposition Matrix"? Above, we've fashioned a crude Venn diagram of the sprawling web of government watch lists. While up-to-date information about each list is notoriously difficult to obtain, this should give you a sense of where Tamerlan fit on the spectrum of suspected terrorists (the diagram is not set to scale).

TIDE

Tamerlan was first placed on TIDE, a massive database controlled by the National Counterterrorism Center, after an FBI interview based on a tip from Russian authorities in 2011 that Tamerlan had become radicalized. The latest information about the size of TIDE's database is from 2008, when it contained more than 540,000 names representing about 450,000 real people (multiple spellings of names inflate the overall number).

Terrorist Screening Database

The next list Tamerlan found himself on, according to Hosenball, was the Terrorist Screening Database, a declassified version of TIDE with fewer details about individual suspects. According to the Washington Post, the Terrorist Screening Database contained more than 400,000 unique names as of 2009. Around the time Tamerlan was placed on this list, he was also placed on a list managed by the Homeland Security Department's Customs and Border Protection bureau, which flagged Tamerlan's visit to Russia in January 2012. Hosenball suspects that this didn't trigger an alarm because the "FBI had not identified him as a threat after the interview." 

Selectee List

The Selectee List is significantly smaller than the previous two (14,000 names) and calls for mandatory secondary screening at airports. Tamerlan was not placed on this list, according to Hosenball.

No Fly List

Even smaller is the No Fly List, which, as of 2011, included about 10,000 people. According to NPR, the No Fly List is for passengers who authorities believe threaten the plane or could be "traveling somewhere to commit a terrorist act or went to a terrorist camp." No one is told whether they're on the No Fly List, so people don't typically find out until they arrive at the airport. By all accounts, Tamerlan was not on the No Fly List.

Disposition Matrix

This is the list you really don't want to be on. No one knows exactly how large the Disposition Matrix is, but it's the second iteration of the White House kill list and it "spells out the intelligence on targets and various strategies, including contingencies, for handling them," according to reports. For some, "handling" includes a lethal drone strike. Tamerlan is not believed to have been on the matrix.

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Could John McCain's roadmap for intervening in Syria work?

Amid international accusations of chemical weapons use by Assad government forces in Syria's civil war, Secretary of State John Kerry told NATO members on Tuesday that the alliance should consider contingency planning and prepare for possible threats to NATO nations emanating from Syria, including chemical weapons threats (after Kerry's remarks, NATO Secretary-General Anders Fogh Rasmussen clarified that NATO is not considering intervening in Syria).

Earlier this year, however, NATO did deploy three Patriot missile batteries in Turkey, a NATO state, in response to concerns in Ankara that southern Turkish cities could be targeted by Syrian Scud missiles. Other NATO countries are acting independently to facilitate arms provisions, non-lethal supplies, and training for rebels. And earlier this month, Pentagon officials announced they were doubling the U.S. military presence in Jordan to 200 military planners, with the potential to expand that presence to as many as 20,000 soldiers in an emergency.

In Washington, meanwhile, there is a mounting policy debate about the "least bad" options for the United States in responding to the protracted conflict in Syria. In a policy speech delivered last week, Sen. John McCain, a consistent advocate of intervention in Syria, outlined potential options for U.S. involvement in the conflict:

No one should think that we have to destroy every air defense system or put tens of thousands of boots on the ground to make a difference in Syria. We have more limited options. We could, for example, organize an overt and large-scale operation to train and equip Syrian opposition forces. We could use our precision strike capabilities to target Assad's aircraft and Scud missile launchers on the ground, without our pilots having to fly into the teeth of Syria's air defenses. We could use similar weapons to selectively destroy artillery pieces and make their crews think twice about remaining at their posts. We could also use Patriot missile batteries outside of Syria to help protect safe zones inside of Syria.

So, is McCain on to something? Could his options serve as blueprints for intervention? The United States already operates a clandestine training program for Syrian rebels in Jordan, and growing the program could be a "very significant gamechanger," Jeffrey White, defense fellow at the Washington Institute of Near East Policy, told FP.

Precision strikes, while feasible, would require "something like a mini-campaign" with a dedicated effort to find targets, some of which may have to be struck multiple times, White said. "It couldn't be done in one fell swoop."

Joshua Landis, a professor at the University of Oklahoma who has consulted for the administration, suggests on his blog, Syria Comment, that the Obama administration may be receptive to the idea of Patriot-enforced safe zones:

For some time, the language used in the White House to frame the Syria problem has been that of containment. Here are some of the oft repeated phrases I have been hearing from White House insiders:

  • "Keep the violence inside Syria"
  • "Cauterize"
  • "Prepare for Syrian failure"
  • "Shore up the neighbors"
  • "There are no good guys in Syria"

Adm. James Stavridis, the supreme allied commander for Europe, told the Senate Armed Services Committee last month that, in his opinion, Patriot-enforced no-fly zones along Syria's northern border "would be helpful in breaking the deadlock and bringing down the Assad regime."

"Assuming we have permission to deploy Patriot missiles appropriately in Turkey and Jordan, they could be used to implement a no-fly zone," White told FP, though he pointed out that the density of the fighting in southern Syria would limit the effectiveness of a no-fly zone in establishing a buffer zone along the Jordanian border.

There is a potential downside to establishing safe zones, though. White pointed to the potential for retaliation, saying, "If you had Patriot missiles trying to enforce a no-fly/no-missile zone, they could be targeted. There could be some risk to these forces, I wouldn't say significant risk, but some risk." Landis also cites concerns raised by David Pollock, also of the Washington Institute for Near East Policy, that safe zones, depending on how they're enforced, could lead to blowback. Bill Frelick of Human Rights Watch has also suggested that buffer zones could trap refugees in the war zone without access to necessary aid.

What's clear is that President Obama is now facing increased pressure to act in Syria based on comments made in Israel last month that the use of chemical weapons would be a "red line." What comes after that red line's been crossed? Well, that's far less certain.

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