RUTHFULLY YOURS

On Dec. 7, 1941 the United States suffered the worst intelligence failure in its history—before or since—when Japanese planes destroyed much of the U.S. Pacific Fleet at Pearl Harbor.

The most astounding aspect of the Pearl Harbor attack was that the U.S. had already broken the Japanese code and was listening to its communications. The U.S. had hundreds of cryptologists and linguists, mostly from the Navy, listening to Japanese wireless communications. But it wasn’t enough. “We knew something was going to happen on Sunday, December 7th at around noon Washington time,” Henry Kissinger said at a speech I attended two years ago in New York City. “The problem is that nobody knew that when it’s noon in Washington, it’s around 7 a.m. in Hawaii.”

In other words, despite being on a war footing with Japan and knowing from intercepted communications that the Japanese were planning for a significant event to affect Japanese-U.S. relations that Sunday, our government couldn’t conceive of—and didn’t defend against—an attack on its largest Pacific naval facility, Pearl Harbor.

This was a failure to think outside the box, coupled with a strong belief that the Japanese were inferior and incapable of mounting such an attack. Eight U.S. battleships, three cruisers and three destroyers were either damaged or sunk, 188 aircraft were destroyed (almost all on the ground), and 2,402 Americans were killed. All of this was accomplished in 90 minutes with 353 small Japanese planes.

Twenty years earlier in a highly publicized demonstration, Gen. Billy Mitchell had proven the vulnerability of naval vessels to airplanes in the waters off Virginia. In July 1921, Mitchell’s planes sank a surplus German destroyer, a light cruiser and the battleship Ostfreisland in full view of hundreds of visitors who were brought to see the exercise.

One of those visitors was Osami Nagano, a Japanese naval captain who was part of Japan’s diplomatic corps. Nagano clearly understood the demonstration’s implications. But the U.S. wasn’t in the mood for military spending after World War I, when a strong sense of isolationism took hold of the country.

Just as the lessons of Vietnam shaped today’s U.S. military, the lessons of Pearl Harbor shaped our armed services through the 1960s. In 1942, only months after the attack, then-Colonel Curtis LeMay was forced to take ill-trained troops into combat and watched hundreds of them die. He never wanted to see the U.S. in that position again, a goal that guided his creation of the Strategic Air Command—America’s nuclear punch—during the earliest years of the Cold War.

LeMay understood that in a nuclear war the U.S. wouldn’t have the luxury of two years to build the Army, Navy and Air Force that it needed in World War II but didn’t yet have in December 1941. LeMay drilled into his crews the idea that their first mission might well be their only mission, which is why they had to be constantly prepared. Partly because of that strength, there was never a nuclear exchange between the U.S. and U.S.S.R.

Seventy years after Pearl Harbor, the U.S. finds itself in much the same situation that it was in prior to World War II. There is a great effort to cut military spending, bring troops home from abroad, and scale back our international exposure. The country’s critical financial situation is one reason. Yet a nuclear-obsessed Iran, an emerging China and Russia, along with smaller rogue actors are enough of a threat to justify a vigilant and even aggressive guard. Add to this the weariness of two prolonged wars in Afghanistan and Iraq and the comparison is complete.

Two weeks ago, National Public Radio’s “All Things Considered” examined Republican presidential candidate Newt Gingrich’s statement of concern about the possibility of an “EMP” attack on America. That’s an electro-magnetic-pulse attack—a huge shock wave of electricity that could come from a nuclear weapon detonated high in the atmosphere above the homeland. Such a wave could destroy the country’s electrical grid, stop almost all cars and trucks, cause sewage to back up in every city, and disrupt the food and water supply—essentially sending us back 250 years.

NPR’s guest, Wired magazine reporter Noah Shachtman, was skeptical. He called Mr. Gingrich a “charter member” of the “professional EMP, scare-monger, worry-wart crowd,” and he wondered if it really made any sense that “Iran or North Korea or some other country is going to be so mad at us” that they would actually do something like this.

The doubters may indeed be right. But 70 years ago similar doubters believed Japan would never be so foolish as to take on the United States of America—until, of course, it did.

Mr. Kozak is the author of “LeMay: The Life and Wars of General Curtis LeMay” (Regnery, 2009).