In July 2013 I had the privilege to sit down with staffers from the office of U.S. Rep. Candice Miller. Miller is the powerful chairwoman of the House Subcommittee on Border and Maritime Security, the vice chair of the House Committee on Homeland Security, and a vocal border hawk. In 2013 she co-authored the “Border Security Results Act,” a bill that would have been incorporated into (or replaced) the House’s Comprehensive Immigration Reform bill. Among other things, the Border Security Results Act would have mandated that the Department of Homeland Security accomplish 100% “situational awareness” and a 90% interdiction rate along both the southwest and northern U.S. land borders before certain other legal reforms (including the much-vaunted ‘pathway to citizenship’ for undocumented workers) could be enacted.
My encounter with Miller’s staff took place alongside a group of activists following a protest outside her office, part of a National Day of Action Against Border Militarization organized by Latino civil rights groups. Miller’s staffers were kind enough to invite the group of us inside, offer us water and discuss our concerns. During the course of our conversation, a staffer and I began to debate the merits of additional spending on “border security” infrastructure and technology, in this case along the U.S./Canada border. Bewildered by my reservations, the staffer insisted “the northern border is vulnerable. We have known cases of terrorists trying to come in from Canada. When we talk to officials from Homeland Security they tell us that the northern border is wide open!” Another activist piped up, challenging the staffer: “do you have any evidence to suggest that ‘terrorists’ are actually attempting to enter the United States from Canada?” to which the staffer, by now exasperated, responded “well, do you have any reason to believe that they are not?” 
I want to reflect on this exchange for a moment. At the time, the staffer’s comment struck me as deeply resonant with another well-known formulation by former Secretary of Defense Donald Rumsfeld, who, in 2002, in response to a reporter’s request that he produce specific evidence backing up his insinuation of a link between then-Iraqi president Saddam Hussein and the Al Qaeda terrorist network, stated:
“Reports that say there’s — that something hasn’t happened are always interesting to me, because as we know, there are known knowns; there are things that we know that we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns, the ones we don’t know we don’t know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones…”
Filmmaker Errol Morris recently undertook a breathtaking deconstruction of the epistemology reflected in Rumsfeld’s statement. Yet despite debates as to its faults or merits, I think it would be misleading, at best, to consider Rumsfeld’s formulation to be a deviation or outlier from the logic informing much post-9/11 governmental practice. Indeed, Rumsfeld himself is among the primary architects of this policy world.
Following Rumsfeld’s logic, it is not so much an identifiable or articulated threat that provokes the mobilization of a governmental response, but the mere possibility that an unknown threat may exist in the present or materialize at some unspecified point in the future.  And it is the fact that we do not know whether this threat exists, what it might be or when it might materialize that is viewed as an existential vulnerability. This logic, then, mandates and justifies an endless expansion of surveillance, data collection, and – as scholars like Anderson and Massumi have discussed – pre-emptive military and police intervention. 
Consider, for example, the National Security Agency’s expansive networks of surveillance, including the bulk warrantless collection and monitoring of internet communication, device location records, text messages, financial transactions, private webcam images and phone call metadata, as recently exposed by former NSA-contractor Edward Snowden. Or, consider the theatrical, invasive search of passengers on all U.S. and international flights, and the fantastic logic that informs this investigative activity (full body scans, the removal of shoes, the banning of liquid in quantities greater than 3.4 ounces – all because an individual could, theoretically, use these as a medium to deliver an explosive onto an airplane – and it is not known whether anyone will do so).
Enforcement efforts along the U.S./Mexico and U.S./Canada borders indicate how the imperative to collect ever-greater volumes of data is not just an epistemological, logistical or technological problem, but also a spatial one. In the border region, the drive toward expansive surveillance and policing manifests through a seemingly endless proliferation of Homeland Security presence in urban neighborhoods, along transportation corridors, and in remote rural, wilderness and sovereign tribal areas. Already, since September 11, 2001 $100 billion has been spent on border security operations, and the combined budget of U.S. Customs and Border Protection and Immigration and Customs Enforcement now outpaces all other federal law enforcement combined.
Yet despite these efforts, the U.S. Department of Homeland Security still faces significant challenges and limitations on where and how effectively it is able to collect data on and intervene in activity taking place in and through the borderlands. Indeed, in 2012 the U.S. Government Accountability Office estimated that only about 15% of the United States’ southwest border met the agency’s highest threshold classification for “operational control” (a metric that indicated the Border Patrol’s ability to continuously monitor, detect, respond to and successfully interdict unlawful incursions into U.S. territory, with “a high probability of apprehension upon entry”), while only 0.8% – or 32 miles – of the United States’ northern border met this threshold. 
On the one hand, such figures shouldn’t be surprising. The Border Patrol is mandated to police not only the 1,954 mile or 3,987 mile-long linear U.S./Mexico and U.S./Canada borders, but also an area up to 100 miles inland from these borders (along with the United States’ coastal borders), a voluminous area of hundreds of thousands of square miles that includes two-thirds of the United States’ population. Meanwhile, much of the land along the U.S./Mexico and U.S./Canada borders, where the Border Patrol maintains its most active presence, is extremely remote and inaccessible, lacking the most basic infrastructure. In the course of fieldwork I have often witnessed DHS officials describe the challenges these conditions pose to their operations. The following two excerpts from a panel discussion on border technologies, involving U.S. Border Patrol Big Bend Sector chief John Smontana and Nogales Station chief Leslie Lawson, are exemplary. Describes Smontana:
“Big bend is a uh, one quarter of the entire southwest border, we have 510 border miles and 165,000 square miles of territory, ten stations, two sub-stations and 4 permanent checkpoints… You can see what some of our territory looks like, its very remote, its very rugged, uh, it’s hard to get to the border in most places. If you leave many of our stations it may take 5 to 6 hours just to reach the border in that area… in most of the areas off the roads, uh, there’s no cell coverage in our area… uh, and the further away from the border, to the interior you get, there’s also a lack of radio repeaters and such so uhm, for us it’s just the general remoteness of the area, there’s no infrastructure of any type”
“Like Del Rio and Big Bend one of our biggest challenges is communications, is getting the sensor, the sensor signals back to our repeaters which can get, then get back out to our dispatch. Uhm I have, we have our own dispatch center down in Nogales uhm, at the station and we have a very difficult time, frankly, in our west area especially, what we call “Zone 19,” getting any signals whatsoever back… uhm, and, out in the Tumacacori highlands… the infrastructure out there, you’re not going to find a celltower, you’re not going to find a tele, you know, a telephone tower, the one repeater that we have out there in that area is a solar repeater, and they literally had to bring by helicopter all of the pieces, that uh, to repair that, to set it up and repair it, so when that repeater goes down for us it’s pretty critical, uhm, and agents have a difficult time, uh communicating out there in our west area.” 
As indicated by Smontana and Lawson, among the primary challenges to the Border Patrol’s operations is the sheer volume and remote condition of the landscape that agents are charged to police. Many areas lack any surveillance capability whatsoever. Even when surveillance technology is successfully deployed, there are often difficulties with the strength and reliability of communications signals. And even when signals are successfully transmitted, agents still face issues of navigation and safety accessing mountainous areas that lack roads or other infrastructure.
The above problems persist despite a massive security buildup that over the past decade has transformed many areas of the borderlands, including the construction of thousands of miles of new roads; the erection of hundreds of miles of vehicle barriers and single and double-layer fencing; the investment of billions of dollars in ground radar, spy towers and other “virtual fence” technologies; the proliferation of internal vehicle checkpoints where all passing motorists must establish their citizenship and submit to inspection; a series of “hiring surges” that have made U.S. Customs and Border Protection the largest law enforcement agency in the United States – and encounters with (and scrutiny from) Border Patrol agents a ubiquitous daily reality for many border area residents; and the domestic deployment of unmanned aerial vehicles, military aerostats and U.S. spy satellites to gather visual data on unauthorized crossing patterns. In order to accomplish the above measures, Homeland Security officials have had to disregard numerous civil and human rights protections; engage in highly invasive search and surveillance practices; and wave a total of 36 environmental and cultural preservation laws.
Nevertheless, Congressional security advocates like Miller have seized on figures like the 2012 GAO statistic referenced above, and used these as a battering ram against DHS and Obama administration officials to argue that they are unserious about their border enforcement mandate. By extension, the U.S. congress has proposed various new security metrics and enforcement schemes. In 2013 these included S.744, the Senate’s Comprehensive Immigration Reform bill, which would have expanded the Customs and Border Protection budget by $48 billion; mandated 700 miles of new fencing; added sufficient additional UAVs to the CBP arsenal to allow the Border Patrol to monitor the border “24 hours per day and for 7 days per week;” and hired an additional 18,000 Border Patrol agents, almost doubling the size of the agency for the third time since 1994. Meanwhile, H.R.2278, the “Strengthen and Fortify Enforcement Act,” would have massively expanded the grounds for removal and criminal penalties associated with unauthorized entry. And, as discussed above, Miller’s “Border Security Results Act,” would have mandated the accomplishment of real-time surveillance and a 90% “effectiveness rate” (defined as the proportion of the total number of detected unauthorized border crossers that the Border Patrol is able to successfully interdict or “turn back”) across both of the United States’ land borders. Congressional gridlock over the federal immigration overhall led each of these proposals to fizzle out. But congressional inaction has not curbed the ambitions of DHS officials. Stated U.S. Border Patrol chief Michael Fisher to a crowd of Homeland Security contractors in October 2013:
“…for the past ten years or so in the department we’ve really been limited in our ability to gain situational awareness. Matter of fact we were very confident and proud each and every reporting cycle to tell you what we did know. We said because we’ve got thousands of Border Patrol agents here, we have unattended ground sensors. We actually have, uhm, remote video surveillance systems. We know what is happening in this particular area. And they say well what about places where you don’t have that stuff. Well we don’t know we don’t know, we can’t get out there so, really, you know, give us a break. We recognized within this new strategy [the Border Patrol’s 2012-2016 National Strategic Plan] and implementation we had to shore that gap up somehow.
Fisher goes on to describe an exploratory effort to use U.S. geo-spatial intelligence collections and big data processing capacities to detect visual anomalies in remote border locations – anomalies that could indicate signs of unauthorized movement, but that will require extensive and ongoing effort to “ground truth.” Fisher concludes by stating:
“But I think that people understand that at a minimum 90% effectiveness, I believe – and I’ve testified to this – that it is achievable as a strategic objective. And how we get there, it’s going to be more and more of the technology, it’s not going to be a doubling or tripling of the size of the Border Patrol. And that’s my operational perspective on it” 
Yet any shortcoming in the above effort, any limitation on the United States’ ability to detect or interdict unauthorized crossers, can inevitably be used by security advocates to argue for greater resources, infrastructure, technology and legal authority. This is because, according to former U.S. Customs and Border Protection commissioner W. Ralph Basham: “You’ve got people coming at you that you don’t know, you don’t know what they represent. It could be that day worker, or it could be a terrorist, or it could be a cartel smuggling drugs or people.”  At the same time, if we take seriously the logic of the “unknown unknown” (literally, according Rumsfeld, any threat to the United States that can be imagined), there will remain, in principle, no limit to the expansion of the surveillance and police operation – because the scope of phenomena and volume of data beyond the present capacity of U.S. authorities to observe, meaningfully interpret and respond to is, in principle, infinite – whereas a threat posed as hypothetical can never be ameliorated.
It remains, of course, important that scholars study the effects of this cyclical logic on border communities, and on U.S. society more broadly. Among others, these include the disruption of everyday life and commerce for residents and travelers in the border region; disproportionate policing and incarceration rates for border communities – particularly indigenous and Xicano youth; whole communities – particularly undocumented residents and mixed-status families – living in fear of deportation; damage to wildlife corridors, riparian habitat and wilderness areas; civil and human rights abuses committed against immigrants and U.S. citizens alike; and, worst of all, thousands of deaths of unauthorized migrants, as border crossers move to increasingly remote and difficult areas to avoid the reach of the Border Patrol.
There is also a need to work theoretically through the profound mismatch between Congressional and DHS security advocates’ tactical ambitions and the many quotidian challenges they face in pursuing these goals. Such challenges include the environmental and geographical conditions that render surveillance, communication and navigation costly and difficult. Sundberg’s (2011) discussion of the importance of non-human entities to explanation of the geography of boundary enforcement is useful for thinking about the many conditions, forces and actors that complicate and unravel even the most sophisticated government interventions.  The efforts of scholars like Elden (2013) and Gordillo (2013) to theorize terrain, as a military-strategic concept distinct from the political-juridical concept of territory or the political-economic concept of land, offer another possible path forward.  Writes Gordillo:
“the spatial texture of the planet demands new conceptual tools to account for the volumetric physicality of space and for the ways in which its forms, folds, and multiplicity preclude vision and the deployment of violence. I believe that the concept of terrain is key to this theoretical shift because this is the only term that indicates that, indeed, space is made up of forms, folds, textures, depths, and volumes.” (emphasis in the original)
Politically, it is imperative that critics of the Homeland Security build-up understand and challenge the logic that animates its operation. Without a reassessment of the composition of “threat” and its mobilization by U.S. authorities, it will remain difficult to address the damaging consequences of the Homeland Security buildup along the border, let alone curb its ongoing expansion. This work, of course, must be complemented by broad-based, popular movements fighting back against the disruption of border policing on peoples’ lives and communities, as is currently being pursued by residents of Arivaca, Arizona; by undocumented workers in South Tucson; and by members of the Tohono O’odham Nation. Without such political and theoretical work, the militarization of U.S. borders is prone to proceed apace.
Geoff Boyce is a PhD candidate in the School of Geography and Development at the University of Arizona. He conducts research and writes on homeland security and immigration-related issues in the United States. His work can be accessed at the hyperlink above and he can be reached at gboyce [at] email.arizona.edu.
 field note, July 2013
 Rumsfeld’s “unknown unknown” is an important departure from the logic governing, say, traditional police work, or the criminal justice system. In the case of the former, an officer may only make a detention or arrest if a) that officer knows that a crime has been committed, and that a targeted individual is likely to be the person who committed that crime. Police in the United States are constitutionally prohibited from making an arrest merely on a hunch or for preemptive reasons. On the other hand, within the criminal justice system, prosecutors work to piece together evidence revealing a chain of events, motive and culpability. Every piece of the puzzle (a witness, call log or a fingerprint left at the scene of a crime) might presumably lead to additional information that might help reconstruct a particular crime and contribute to an individual’s conviction.
 See Anderson, B (2010) Preemption, precaution, preparedness: anticipatory action and future geographies. Progress in Human Geography 34:777–798; Massumi, B (2010) The future birth of the affective fact: the political ontology of threat. in Gregg, M and Seigworth, GJ (eds.) The Affect Theory Reader Durham: Duke University Press 2010
 U.S. Government Accountability Office (2012) Border Patrol Strategy:Progress and Challenges in Implementation and Assessment Efforts. published 8 May 2012, Washington, D.C. http://www.gao.gov/products/GAO-12-688T
 field note, October 2012
 field note, October 2013
 Basham’s statement was broadcast as part of PBS’s three part Need To Know series on the U.S. Border Patrol, http://www.pbs.org/wnet/need-to-know/video/video-crossing-the-line/14291/
 Sundberg, J. (2011). Diabolic Caminos in the Desert and Cat Fights on the Rio: A Posthumanist Political Ecology of Boundary Enforcement in the United States-Mexico Borderlands. Annals of the Association of American Geographers, 101, 318-336.
 See Elden, S. (2013). Secure the Volume: Vertical Geopolitics and the Depth of Power. Political Geography, 34, 35-51; Gordillo, G. (2013). Opaque Zones of Empire. Space and Politics: Essays on the Spatial and Affective Pulse of Politics. 25 June 2013. http://spaceandpolitics.blogspot.ro/2013/06/opaque-zones-of-empire_25.html.