This arm of the US government is often referred to with a three- letter acronym. Headquartered in suburban Virginia, it's functioned as the country's largest intelligence organization since its founding in the wake of World War II.
CIA? No, DOD. The Department of Defense controls some 80 percent of the nation's intelligence budget - and therein lies a large complication for the prospects of intelligence reform.
In recent days Pentagon officials have publicly cautioned against shifting too much budget power to a new national intelligence director. Among other things, they worry that a new layer of bureaucracy might block critical tactical intelligence from reaching warfighters in time.
Such complaints shouldn't be breezily dismissed, say experts. There's a reason DOD spends so much on intelligence - gathering information about adversaries is a basic activity for all the armed services.
And the Pentagon is Washington's wiliest and most powerful bureaucracy. If it feels it's lost too much control over such intelligence subsidiaries as the eavesdropping National Security Agency (NSA), it may just rebuild capability in-house, at great expense.
"I think you'll see the services creating their own new NSA, their own new imagery agency. You're going to just end up with a big mess," predicted Gen. William Odom, former NSA director, at a House Armed Services Committee hearing last week.
That's not what members of the 9/11 commission believe will happen. They say the proposed reforms are simply meant to ensure greater cooperation among the government's 15 intelligence agencies.
The establishment of a new National Intelligence Director (NID) should not interfere with military operations, they say, even if that person has the power to move money in and out of budget accounts previously controlled by the Pentagon.
Under the commission's recommendations, a top Defense Department official would serve as one of the new NID's deputies. Control of tactical, or battlefield, intelligence would remain in the hands of military agencies.
"It is unimaginable to us that the national intelligence director would not give protection of our forces deployed in the field a very high, if not the highest, priority," 9/11 commission vice chairman Lee Hamilton told a House panel last week.
Nor do Pentagon officials say that they adamantly oppose the commission's proposed changes. But they want to proceed with caution, so that any new national intelligence organization takes DOD concerns into account.
"There needs to be an awful lot of flexibility if we're going to meet the military missions," Adm. Lowell Jacoby, director of the Defense Intelligence Agency, told the House Armed Services Committee last week.
But budget control equals power in Washington, and any proposal that affects the federal city's balance of power is bound to run into resistance. In this context, it is the Pentagon, not the CIA, that has the most to lose from intelligence reform.
The CIA's recruitment of spies and its foreign espionage is a dangerous and important business, but it's not nearly as expensive as, say, maintaining a network of spy satellites - a Pentagon-run activity.
Such satellites are an invaluable source of strategic, national-level intelligence on such things as the possible location of Al Qaeda leaders. But they're also useful for such tactical battlefield needs as the position of Shiite militias in Najaf.
"There are functional reasons that much of the intelligence budget is under the control of the Department of Defense, and the [9/11 commission] does not address these issues and trade-offs," says Anthony Cordesman, senior fellow at the Center for Strategic and International Studies, in a report on the commission's proposals.
The reform proposals may call for battlefield intelligence to remain a purely military concern, but it's not always easy to separate the tactical from the strategic, say Pentagon officials. National Security Agency spy satellites, for instance, provide the Air Force with information about the location of surface-to-air missile systems, enabling Air Force controllers to route unmanned Global Hawk aerial vehicles around potential threats.
Many of the Army's tanks and Bradley Fighting Vehicles have transponders that warn friendly forces where they are. But that equipment uses strategic-level communications satellites to send its data back to headquarters - another clear example of intelligence overlap.
"The interconnection is at this point very difficult for us to now begin to break apart," Undersecretary of Defense for Intelligence Stephen Combone told the House Armed Services panel.
Whether the DOD will in fact lose control over the National Security Agency, the Defense Intelligence Agency, remains an open question. Many Democrats, including presidential candidate John Kerry, have backed the 9/11 commission's ideas and urged quick action. President Bush, for his part, has embraced the idea of appointing a national intelligence director, albeit one without the wide-ranging budgetary powers the 9/11 panel envisioned.
"Reform is never easy. You've got a lot of entrenched interests there," President Bush said at a campaign stop in Florida last week.