As Mr. Hashimoto spoke, sirens began to wail, in one of the routine checks of emergency-response systems that this town of almost 18,000 residents has held since the accident in March at the Fukushima Daiichi plant, 36 miles away. Officials also regularly measure the fallout that has blown this way from the stricken plant, though they say radiation levels are not high enough to endanger health.

Still, the irony of Ishikawa’s current predicament has proven rich enough to draw renewed attention to Japan’s wartime atomic bomb programs, which are not well known here.

The programs were revealed soon after the war, but for decades Ishikawa’s role went largely unnoticed, as an economically resurgent Japan tried its best to put its wartime past behind it. Since the 1990s, major media have become less inhibited about discussing the war, including Japan’s atomic bomb programs. However, the programs still seem to be easily forgotten in a nation that is more accustomed to thinking of itself as the victim of the deadly American atomic attacks on Hiroshima and Nagasaki.

Mr. Ariga, who in recent years has begun telling his story to local schoolchildren, says that most Japanese are shocked to hear that their nation also tried to build an atomic bomb. “I have no doubt Japan would have used it if it succeeded,” he added.

Historians say Japan never got as far as even designing, much less actually building, an atomic weapon. Indeed, its wartime efforts can seem woefully insufficient for the task: in Ishikawa, about 130 schoolchildren were put to work digging for uranium ore because the adult men had all been sent off to war.