The document describes a constellation of spy agencies that track millions of surveillance targets and carry out operations that include hundreds of lethal strikes. They are organized around five priorities: combating terrorism, stopping the spread of nuclear and other unconventional weapons, warning U.S. leaders about critical events overseas, defending against foreign espionage, and conducting cyber-operations.

In an introduction, Clapper said the threats facing the United States "virtually defy rank-ordering." He warned of "hard choices" as the intelligence community - sometimes referred to as the "IC" - seeks to rein in spending after a decade of often double-digit budget increases.

The current budget proposal envisions that spending will remain roughly level through 2017 and amounts to a case against substantial cuts.

"Never before has the IC been called upon to master such complexity and so many issues in such a resource-constrained environment," Clapper wrote.

An espionage empire

The summary provides a detailed look at how the U.S. intelligence community has been reconfigured by the massive infusion of resources that followed the 2001 attacks.

The United States has spent more than $500 billion on intelligence during that period, an outlay that U.S. officials say has succeeded in its main objective: preventing another catastrophic terrorist attack in the United States.

The result is an espionage empire with resources and a reach beyond those of any adversary, sustained even now by spending that rivals or exceeds the levels at the height of the Cold War.

The current total budget request was 2.4 percent below that of fiscal 2012. In constant dollars, it was about twice the estimated size of the 2001 budget and 25 percent above that of 2006, five years into what was then known as the "global war on terror."

Historical data on U.S. intelligence spending is largely nonexistent. Through extrapolation, experts have estimated that Cold War spending probably peaked in the late 1980s at an amount that would be the equivalent of $71 billion today.

The surge in resources for the agency funded secret prisons, a controversial interrogation program, the deployment of lethal drones and a huge expansion of its counterterrorism center. The agency was transformed from a spy service struggling to emerge from the Cold War into a paramilitary force.

The CIA has devoted billions of dollars to recruiting and training a new generation of case officers, with the workforce growing from about 17,000 a decade ago to 21,575 this year.

The agency’s budget allocates $2.3 billion for human intelligence operations and $2.5 billion to cover the cost of supporting the security, logistics and other needs of those missions around the world. A relatively small amount of that total, $68.6 million, was earmarked for creating and maintaining "cover," the false identities employed by operatives overseas.

There is no specific entry for the CIA’s fleet of armed drones in the budget summary, but a broad line item hints at the dimensions of the agency’s expanded paramilitary role, providing more than $2.6 billion for "covert action programs" that would include,

• drone operations in Pakistan and Yemen

• payments to militias in Afghanistan and Africa

• attempts to sabotage Iran’s nuclear program

The black budget illuminates for the first time the intelligence burden of the wars in Afghanistan and Iraq. For 2013, U.S. spy agencies were projected to spend $4.9 billion on "overseas contingency operations."

The CIA accounted for about half of that figure, a sum factored into its overall $14.7 billion budget.

Those war expenditures are projected to shrink as the United States withdraws forces from Afghanistan. The budget also indicates that the intelligence community has cut the number of contractors it hires over the past five years by about 30 percent.

Critical gaps

Despite the vast outlays, the budget blueprint catalogues persistent and in some cases critical blind spots.

Throughout the document, U.S. spy agencies attempt to rate their efforts in tables akin to report cards, generally citing progress but often acknowledging that only a fraction of their questions could be answered - even on the community’s foremost priority, counterterrorism.

In 2011, the budget assessment says intelligence agencies made at least "moderate progress" on 38 of their 50 top counterterrorism gaps, the term used to describe blind spots. Several concern Lebanon’s Hezbollah movement, an enemy of Israel that has not attacked U.S. interests directly since the 1990s.

Other blank spots include questions about the security of Pakistan’s nuclear components when they are being transported, the capabilities of China’s next-generation fighter aircraft, and how Russia’s government leaders are likely to respond to,

"potentially destabilizing events in Moscow, such as large protests and terrorist attacks."

A table of "critical" gaps listed five for North Korea, more than for any other country that has pursued or is pursuing a nuclear bomb.

The intelligence community seems particularly daunted by the emergence of "homegrown" terrorists who plan attacks in the United States without direct support or instruction from abroad, a threat realized this year, after the budget was submitted, in twin bombings at the Boston Marathon.

The National Counterterrorism Center has convened dozens of analysts from other agencies in attempts to identify "indicators" that could help law enforcement officials understand the path from religious extremism to violence. The FBI was in line for funding to increase the number of agents who surreptitiously track activity on jihadist Web sites.

But a year before the bombings in Boston, the search for meaningful insight into the stages of radicalization was described as one of the "more challenging intelligence gaps."

High-tech surveillance

The documents make clear that U.S. spy agencies’ long-standing reliance on technology remains intact.

If anything, their dependence on high-tech surveillance systems to fill gaps in human intelligence has intensified.

A section on North Korea indicates that the United States has all but surrounded the nuclear-armed country with surveillance platforms. Distant ground sensors monitor seismic activity and scan the country for signs that might point to construction of new nuclear sites. U.S. agencies seek to capture photos, air-samples and infrared imagery "around the clock."

In Iran, new surveillance techniques and technologies have enabled analysts to identify suspected nuclear sites that had not been detected in satellite images, according to the document.

In Syria, NSA listening posts were able to monitor unencrypted communications among senior military officials at the outset of the civil war there, a vulnerability that President Bashar al-Assad’s forces apparently later recognized. One of the NRO’s functions is to extract data from sensors placed on the ground near suspected illicit weapons sites in Syria and other countries.

Across this catalogue of technical prowess, one category is depicted as particularly indis­pensable: signals intelligence, or SIGINT.

The NSA’s ability to monitor e-mails, phone calls and Internet traffic has come under new scrutiny in recent months as a result of disclosures by Snowden, who worked as a contract computer specialist for the agency before stockpiling secret documents and then fleeing, first to Hong Kong and then Moscow.

The NSA was projected to spend $48.6 million on research projects to assist in "coping with information overload," an occupational hazard as the volumes of intake have increased sharply from fiber-optic cables and Silicon Valley Internet providers.

The agency’s ability to monitor the communications of al-Qaeda operatives is described in the documents as,

"often the best and only means to compromise seemingly intractable targets."

Signals intercepts also have been used to direct the flight paths of drones, gather clues to the composition of North Korea’s leadership and evaluate the response plans of Russia’s government in the event of a terrorist attack in Moscow.

The resources devoted to signals intercepts are extraordinary.

Nearly 35,000 employees are listed under a category called the Consolidated Cryptologic Program, which includes the NSA as well as the surveillance and code-breaking components of the Air Force, Army, Navy and Marines.

The NSA is planning high-risk covert missions, a lesser-known part of its work, to plant what it calls "tailored radio frequency solutions" - close-in sensors to intercept communications that do not pass through global networks.

Even the CIA devotes $1.7 billion, or nearly 12 percent of its budget, to technical collection efforts, including a joint program with the NSA called "CLANSIG," a covert program to intercept radio and telephone communications from hostile territory.

The agency also is pursuing tracking systems,

"that minimize or eliminate the need for physical access and enable deep concealment operations against hard targets."

The CIA has deployed new biometric sensors to confirm the identities and locations of al-Qaeda operatives.

The system has been used in the CIA’s drone campaign. Spending on satellite systems and almost every other category of collection is projected to shrink or remain stagnant in coming years, as Washington grapples with budget cuts across the government.

But the 2013 intelligence budget called for increased investment in SIGINT.

Counterintelligence

The budget includes a lengthy section on funding for counterintelligence programs designed to protect against the danger posed by foreign intelligence services as well as betrayals from within the U.S. spy ranks.

The document describes programs to,

"mitigate insider threats by trusted insiders who seek to exploit their authorized access to sensitive information to harm U.S. interests."

The agencies had budgeted for a major counterintelligence initiative in fiscal 2012, but most of those resources were diverted to an all-hands emergency response to successive floods of classified data released by the anti-secrecy group WikiLeaks.

For this year, the budget promised a renewed "focus... on safeguarding classified networks" and a strict "review of high-risk, high-gain applicants and contractors" - the young, nontraditional computer coders with the skills the NSA needed.

Among them was Snowden, then a 29-year-old contract computer specialist whom the NSA trained to circumvent computer network security.

He was copying thousands of highly classified documents at an NSA facility in Hawaii, and preparing to leak them, as the agency embarked on the new security sweep.

"NSA will initiate a minimum of 4,000 periodic reinvestigations of potential insider compromise of sensitive information," according to the budget, scanning its systems for "anomalies and alerts."

The Black Budget