Arms controllers are an interesting lot. They’re smart, dedicated people — okay, they’re wonky, too — who engage in an arcane pursuit that is vital to U.S. national security.

After all, it’s important to know the strategic capabilities of your enemies, or potential enemies, especially in their most destructive capacities — their nuclear arsenals. That’s why the United States spent decades negotiating with the Soviet Union, and now Russia, to limit and make more transparent both sides’ strategic and tactical nuclear weapons.

That’s why so much attention is paid to Iran and its possible nuclear quest. That’s why nuclear-armed Pakistan is such a worry, and India too. And it’s why the Pentagon watches closely what the Chinese are doing not only with nuclear weapons but also with conventional ballistic missiles: The rockets can threaten, and intimidate, Taiwan and other neighbors.

So it was that arms control experts went apoplectic over a Nov. 30 front-page story in The Post by diplomatic correspondent William Wan, about a research project, conducted by Georgetown University students, into the vast tunnel system that China has built to protect its ballistic missiles and launchers.

The tunnels have been known about for a long time; they’re called the “Underground Great Wall.”

The Chinese use the tunnels to hide, and move, the country’s missiles so that a potential enemy, if it were thinking of attacking China, could never find them all. China would have enough missiles surviving to launch a counter-attack sufficiently damaging to deter the first attack. That’s basic nuclear deterrence.

A 2008 earthquake revealed some of the strategic tunnels. Intrigued by the exposures, a Georgetown professor and Pentagon consultant, Phillip A. Karber, decided to launch a research project with his students. They would use the Internet, Google, Chinese blogs and any other kind of non-classified, open-source intelligence they could find to discover as much as they could about the tunnel system. It was much like a data-mining project that the CIA or National Security Agency might do, except it was done with less powerful computers and cheaper student labor.

Their three-year study concluded that the 3,000-mile Chinese tunnel system is so vast it could hold perhaps 3,000 nuclear warheads, rather than the 200 to 400 that most experts think China probably has.

That sent those who study arms control, well, skyrocketing. In online posts and in letters to me, they blasted Karber, Wan and The Post for having the temerity to suggest that China might have more nuclear warheads than most experts believe. You can read their criticisms on the Federation of American Scientists strategic security blog, ArmsControlWonk and All Things Nuclear.

I think the critics are off the mark.

The Post story didn’t feature the speculative 3,000-warhead figure in the headline, nor in an accompanying graphic; indeed, it didn’t mention the figure until the last section of the story. Moreover, the eighth and ninth paragraphs of the story quote the skepticism with which nuclear experts greeted the study. The story even quoted Karber acknowledging, “I don’t have the slightest idea how many nuclear weapons China really has.”

This wasn’t a story so much on China’s nuclear weapons as it was a story about the amateur sleuthing of two dozen Georgetown students who dedicated their spare time to doing an open-source intelligence study that turned up all sorts of new information on the Chinese tunnel system. The story was more about the students and their team effort than the study’s conclusion.

And that’s why it made for such a good read:It put a human face on an arcane field, and it showed something interesting going on behind the scenes at one of the city’s major universities.

The arms controllers are right that journalists shouldn’t exaggerate the capabilities of America’s enemies. I wrote as much in my column last Sunday on Iran’s nuclear ambitions. But neither should journalists shy away from a fascinating story that looks at something outside the conventional wisdom. That’s one of our jobs.

Patrick B. Pexton can be reached at 202-334-7582 or at For updates, read the omblog at