Without the KMT army beginning to stage large-scale resistance in the Yangtze River Delta in the autumn of 1937, the Japanese army would not have left the vacuum of power in the North China plain, which enabled the Communists to build their bases and expand their influence there.

And without the Communist-led guerrilla warfare in North China, more Japanese troops could have been committed to the attack on the KMT's home base in Southwest China.

Without this strategy, Lu said, it is hard to imagine how a weak, almost anciently agrarian and politically not really unified China could hold out against the far more modernized and ferocious Japanese military for as many as eight years.

The Japanese army commanders aided the tenacious growth in North China's guerrilla war by their own mistakes. They had thought they could easily scare the North China peasants into submission, only to arouse in them a strong national awareness and hatred against the invaders who had plundered their villages and raped and killed their relatives. The invaders then had no way to separate the Communist army, the local resistance forces and village militiamen from the rural masses.

A "people's war" thus became possible when the Communist Party taught the peasants "the techniques of survival", according to a report filed by a US intelligence officer.

In July 1944, 18 professional US intelligence officers, many speaking fluent Chinese, were dispatched to Yan'an, Shaanxi province, the Communist central base during the war, and from Yan'an to other places in North China. It was a mission assigned by President F.D. Roosevelt and General Joseph Stilwell simply because of a lack of information from North China, where heavy Japanese military forces were gathered.

"What they saw was the Communist Party in its best effort to work with the people," Lu said.

Although the US intelligence officers might not fully appreciate the importance of the North China peasants - as the largest source of foot soldiers in many historic wars and regime changes, they did realize that "when the peasants desperately wanted protection and organization, the Communist-led guerrilla war provided them with exactly what they wanted", Lu noted.

Lu and her colleagues found in the reports of 70 years ago "a possibility of not only a different China but also a different version of communism from the Stalinist Russia, and a possibility for the United States to keep playing a role in the changes on horizon," she said.

But as an irony of history, those reports never produced their would-be influence on the policymaking level back in the US, Lu explained. For their matter-of-fact reports, those intelligence officers were forced out of their service and career by a wave of unsubstantiated accusations of subversion and treason amid the McCarthyism in the US in the 1950s.

The reports gathered dust on the shelves in the US archives till now, when they are being used by Chinese historians to construct a more balanced understanding of their nation's past.

The author is editor-at-large of China Daily. edzhang@chinadaily.com.cn