China and Japan may not be on a collision course, but it's not possible to ignore the rhetoric or provocative actions from both sides. The situation is ripe for miscalculation.

It's tempting, in 2014, for historians to replay the debate over the causes of World War 1, with China in the role of expanding Germany and the U.S. as the overstretched British Empire. Had we been thinking more about this last year, we might have looked back at more recent history, to 1983 and a NATO command-and-control exercise called Able Archer.

Few paid much attention to Able Archer at the time. It was part of the routine of military preparedness in a theater where—most people agreed—war could erupt with little notice. What nobody in the West realized was that the Soviet Union was watching it with rising alarm.

The Soviet leadership, including the dying Yuri Andropov, was taking Ronald Reagan's talk of the “Evil Empire” seriously. They no doubt wished that they were as close to building a defensive shield of lasers and particle beams as some U.S. experts thought they were. The Soviets may have surmised that such beliefs could make a preemptive strike tempting. The Pershing II missile, being shipped to Europe in the fall of 1983, looked to them like a decapitation-strike weapon.

Under Operation Ryan, the Soviets had directed the KGB to look for signs of a NATO preemptive strike. KGB agents found what they had been told to find—and as Able Archer started, fears of a NATO attack rose toward the boiling point. It was only when Able Archer stopped as scheduled that the Soviets relaxed their preparations.

Today's intelligence-gathering is no less vulnerable to bias. Japanese China-hawks can look for evidence of China's ambitions to restore the Middle Kingdom's hegemony and find it everywhere, from think tanks to Internet discussion boards. Chinese analysts take note when former Japanese commanders and military-studies academics talk openly about parallels between China's military plans and the Soviet Union's Pacific strategy, and about preparing to defend Japan's outlying islands, as they were doing in Washington in January (see page 64).

Just as the Internet provides echo chambers for the like-minded more easily than it facilitates reasoned debate, it's a place where extreme views can appear to be the consensus, particularly if extreme views are what you are seeking.

Today, reading China's capabilities is complicated by a mix of secrecy about the things that count—readiness, the training level of armed forces, hardware reliability and logistics—and propaganda about new weapons.

Estimates of China's DF-21D anti-ship ballistic missile, as a result, vary enormously, with a hawkish retired Japanese admiral saying it is 10 years away (not because of missile technology but because of the entire kill chain that goes with it) and U.S. analysts suggesting it is close to operational.

The same goes for the J-20 stealth fighter—which one Japanese analyst has compared to the Tu-22M Backfire bomber as an offensive weapon. Are the J-20s seen so far very well-finished prototypes or pre-production aircraft?

On the other side, any Chinese expectations of Japanese passivity—“with a still substantial, if subsurface, warrior ethos opposed by a hyper-sensitive pacifism,” as one U.S. defense official puts it—have been upset by the symbolism of Prime Minister Shinzo Abe's visit to the Yakusuni Shrine.

Abe's visit followed China's declaration of an air defense identification zone over the East China Sea. Nobody could reasonably have failed to see that the establishment of an ADIZ would confirm Japanese hawks' view of China's intent to expand its influence; China probably did not expect such a provocative reaction. That is a disturbing echo of Western intelligence's blindness to the Soviets' nervousness in 1983.

None of this means that war is inevitable. But it is a time for cool heads and—above all—clear and unbiased intelligence.