BEIJING — From the film studios of the Chinese People's Liberation Army comes the biggest blockbuster of them all. Starring Mao Zedong as Chinese communist hero and Gen. Chiang Kai-shek as nationalist villain, "Decisive Battles," a sweeping narrative of the Chinese civil war, is playing to packed houses. Audiences are being taken back to the country's revolutionary roots in a reaffirmation of communist faith. With an all-star cast of almost 300 and battle scenes using 100,000 extras, the six-part movie is the latest attempt by the Communist Party to boost its support. It is all-action propaganda aimed at cynical youth. The Army's image has been soiled by its moves against demonstrators in Tiananmen Square. "We're trying to bring back that revolutionary feeling," said Zhao Yijun, a leading director on "Decisive Battles," the country's most expensive film. "It is to show young people who weren't alive then how arduous it was. The message is: Without the Chinese Communist Party there would be no New China," Mr. Zhao said. Chinese leaders are not unduly alarmed that Chinese communism will be swept away by democratic forces. Their grip on power is solid and the masses are not driven by hunger or shortages. The concern is that pervasive cynicism among the young generation will make the party irrelevant. "Decisive Battles" deals with the three great campaigns of the 1946-1949 civil war, now known as the "Liberation War," that drove the nationalist government, supported by the United States, into exile on Taiwan. The action is spectacular. Twelve tons of explosives were used in one scene alone, sending spumes of mud soaring over a vast battlefield with 100,000 "extras" borrowed from the Army. Work is complete on four parts. Shooting on the last two segments will start next year.