What happens when wartime news gets censored?

Summer officially starts Monday. Are you ready? Have your sunscreen, bathing suit, sunglasses? How about your bottled water, canned food, duct tape, flashlights, extra batteries, and—in case the dirty-bomb fallout drifts in your direction—a prophylactic dose of potassium iodide to ward off thyroid cancer?

Probably not. And yet, here we are, entering the height of travel season with the Homeland Security threat condition at (any guesses?) yellow. Which signifies (any guesses?) "elevated risk."

And elevated risk means … well, any guesses? Really, do you know? Because few of us do. And that's the problem with the Homeland Security Advisory System. We know we're supposed to be on guard, but against what, we're not sure because more specific information is often withheld.

There are good reasons for the government to withhold information from the public, especially in times of war. But when the state censors news this way—whether it's terrorism threats, prison scandals, or torture memos—the impact of doing so must be carefully considered. The costs and benefits of wartime censorship are part of a long-running debate. We are vulnerable when the government keeps secrets from us and sometimes more vulnerable when it does not.

In the first Gulf War, for example, critics complained the news had been sanitized to the point of broadcasting bloodless video-game-like footage of missiles battling missiles. In this war, embedded journalists risk divulging too much. Either way, what is at stake each time we erase the news is not just the nation's security but, more important, our history.

And that's why it's helpful to turn to history for an object lesson, a case of wartime censorship where the issue was much less murky and the results—at first glance, at least—unambiguous. You've likely heard nothing about it. And that, of course, is the problem.

The censored story was one of World War II's oddest, and it involved a fleet of handmade balloons sent east by the empire of Japan. Improbable though it may sound, from late 1944 through the spring of 1945, the Japanese launched more than 9,000 balloons from their nation's eastern shores. Filled not with mild-mannered hot air but extremely flammable hydrogen and armed with incendiary and antipersonnel bombs, the balloons rode the jet stream across the Pacific Ocean for several days before landing throughout North America.

No, really. Throughout North America. From Alaska to Mexico and as far east as suburban Detroit. Perhaps even more incredible, the balloons themselves were not made of any high-tech, weather-hardened fabric but simple paper panels held together with potato glue.

An extraordinary story, right? Irresistible to any reporter and not just because of the balloons themselves, but because of their potential: If a balloon could carry incendiary bombs across the Pacific, without detection or advance warning, what else might travel aboard? Saboteurs? Biotoxins?

Sure enough, stories began to appear. The day after New Year's, 1945, for example, the New York Herald-Tribune carried a brief story about one of the first balloons to arrive. After that, however, even as the balloons were crash-landing at the rate of two or three per day, the nation's media remained largely mum. That's because on Jan. 4, two days after the Herald-Tribune ran its story, the Office of Censorship asked the nation's print and broadcast journalists to report absolutely nothing more about the balloon bombs. And no one did.