One reason the global war on terror is so difficult to comprehend is that, apart from television footage from Iraq, it’s hard to get a visual sense of how the United States is carrying it out.

For that I recommend a trip to the vast mall under Crystal City, Va. Two subway stops from the Pentagon and Reagan National Airport, and a few dead drops from the CIA and FBI, the underground corridors, filled with shops and eateries, serve as a kind of crossroads for players in the shadow war against al Qaeda.

The bustle of this human ant farm replicates what Washington’s Union Station must have been like in 1943, with soldiers, sailors and airmen shipping in from one front and back out to another, bumping into old friends and meeting new ones at tables full of laughter, anger and loss.

You’ll see bright-looking young Special Ops troops, some in their trademark Green Berets, as well as others in civvies, along with civilian intelligence officials and private contractors dangling serious-looking security badges.

Over lunch with a couple fairly well-connected denizens of this world, the news from the front was very good: Lately there has been “unprecedented” cooperation from foreign intelligence services, my lunch companions said, even before news broke of Lebanon’s help in busting an alleged al Qaeda plot to attack New York-area transit lines.

And rival U.S. military and civilian intelligence units, they said, were finally beginning to play nice together in the pursuit and interrogation of al Qaeda operatives — which, if true, would amount to a complete turnaround from the years leading up to Sept. 11, 2001, when the CIA sabotaged a very good FBI investigation of the would-be 9/11 plotters, according to an astonishing account in last week’s New Yorker magazine.

But the billions pouring into the shadow war may not be helping U.S. intelligence get better, these and other insiders say. The investment of vast sums in satellite links, data-mining software and other ultra-sophisticated means of intercepting, tracking, deciphering and translating al Qaeda communications hasn’t measurably improved our knowledge of the enemy.

“I’m weary of all the software talk,” said one high-level former intelligence official who still works closely on counterterrorism. “It can never replace the mastery of foreign culture and languages that a true intelligence service must have.”

While hundreds of millions flow to contractors for new surveillance gizmos and software, a combat battalion in Iraq is lucky to have a single, Arabic speaking intelligence specialist to make quick sense of captured documents and prisoners, my lunch partners said.

Back in Crystal City, meanwhile, the intelligence sections are too often led by military officers with no intelligence experience. They don’t know what they’re looking at.

But most distressing, these sources admit, is that this nation’s intelligence shortcomings are hardly limited to tracking al Qaeda.

Despite over a half century of conflict with it, including a long, hot war, we know few details about North Korea’s leadership beyond dictator Kim John Il and a few of his cronies.

In contrast to Saddam Hussein’s Iraq, where the whole world heard about “Chemical Ali” and “Dr. Germ,” the nicknames U.S. officials bestowed on two of the former regime’s top military scientists, we know almost nothing about the key figures in North Korea’s missile and nuclear weapons programs. None of the sources I checked, including the State Department and Pentagon, on top of hours scouring scholarly journals and books on the topic, revealed much, if anything, about Kim’s inner circle, their roles or reputations.

“No idea,” said a Pentagon spokesman, nearly begging for anonymity, when I asked for the name of Pyongyang’s top rocket man. “It’s hard to know who’s in charge of anything over there.”

My hunch is that if U.S. intelligence knew who runs North Korea’s nuclear and missile programs, by now we’d would have nicknames for them.

“The fact is, we know much too little about North Korea, not for a lack of trying — but technical intelligence can only tell you so much,” Peter Brookes, the Defense Department’s chief of Asian and Pacific Affairs in the first Bush term, told me.

That, evidently, goes double for Somalia, a broken society where, in a serious development that went largely unnoticed last week, a U.S. covert operation against a coalition of Islamic warlords collapsed.

According to news accounts, a U.S. intelligence team in Somalia bet on the wrong horse, opening the door for al Qaeda allies among the warlords to extend their grip from the capital, Mogadishu, north to the Ethiopian border.

There may be serious debate over the extent of al Qaeda’s influence among the warlords, but the growing imposition of Islamic sharia law, along with Osama bin Laden’s recent exhortations to Somali jihadists via audiotape, is not a good sign.

“Black Hawk Down,” it’s turning out, was not the beginning of the end there, only the end of the beginning. One would think that over the decade since the events that inspired the book (and movie), U.S. intelligence could back the right warlord in Somalia, or come up with a better strategy than one that failed so ignominiously before.

Satellites and data-mining software can’t do it for us.

A dearth of U.S. intelligence on Iraq and North Korea must at least partly explain the President’s new, unprecedented diplomatic tack on both problems.

“Whether it be the Iranian issue or the North Korean issue, there is a way forward for these leaders that will lead to a better life for their people and acceptance into the international community,” Bush said at a July 6 press conference in Chicago. “And one of the things we've done in the United States is to work with the [6-power] coalition to send that message [to Kim].”

After conferring with his intelligence chiefs, and sobered by Iraq, the President may know how limited his own options are now, too.

BACKCHANNEL CHATTER

Who knew?

The public’s apparent lack of interest in breathless revelations that U.S. intelligence has been tracking foreign bank transactions may come from a sense that it’s old news — and they are essentially right, former CIA and State Department intelligence analyst Larry C. Johnson says.

Not that this fact would stop the White House’s public relations assault on the New York Times for reporting the story.

But less than a month after the 9/11 attacks, Johnson points out on his “No Quarter” blog [http://noquarter.typepad.com/my_weblog/2006/07/what_secret.html], Rep. Michael G. Oxley , R-Ohio, chairman of the House Financial Services Committee, applauded President Bush and then-Treasury Secretary Paul O’Neill “for taking swift action to block terrorist assets that may be located here in the United States and to warn foreign banks that the U.S. is poised to block their assets in this country and deny th em access to U.S. markets that refuse to freeze terrorist assets overseas.”

Then in Feb. 2002, Treasury official Juan Zarate, now the White House terrorism honcho, testified that al Qaeda operatives were taking precautions to avoid banking tripwires.

Officials have been trooping up to Capitol Hill for five years now to give even more detailed accounts than that, Johnson says, excerpting major bits.

“Only people trading clam shells for coconuts would have been unaware that any financial transaction moving through the international financial system was being scrutinized by the United States government,” he writes.

Jeff Stein can be reached at jstein@cq.com.