Alien aircraft came in low, dropping bombs, firing torpedoes, sending burning ships slipping under the sea. Only this time, the Japanese landed, took over the territory and imprisoned and tortured their new enemies.

From Korea to Hong Kong, from Shanghai to Malaysia and the Philippines, thousands of Americans saw the same thing as people at Pearl Harbor on the eve of World War II. They were missionaries, mining engineers, insurance agents, soldiers of fortune, and sellers of vacuum cleaners. They would become a vital asset to the US war effort. Many would be enlisted as spies.

''They had something we didn't'' says Elizabeth McCalister, an OSS propaganda specialist. ''They knew what was going on.''

The raw intelligence gathered from Americans caught in the Pacific theater on Dec. 7, 1941, and the scary hours and days that ensued are among 3 million files released by the CIA in the past two years. The release, part of the biggest declassification program in US history, was ordered by President Clinton to unlock the remaining secrets about World War II war crimes.

Pearl Harbor is an iconic American moment, a combination of Custer's careless last stand and the Alamo's hopeless heroics. But these newly unveiled, first-person reports are a vivid reminder that the raid that pushed the United States into the war was only one component of Japan's primary goal: conquering Asia.

They also show, for the first time, the enormous amount of precise intelligence that was gleaned from expatriates about how quickly the Japanese seized factories, set up communications, enslaved laborers in its new territories, and how sustaining that expanded empire was making it vulnerable.