Ureo Egawa is a civil engineer assigned to build a road in China. There are three obstacles: the unwilling labor force of local peasants; the weather, which often releases torrential rains to wipe away all the work; and worst of all,communist bandits. He works unflaggingly for the good of Greater Asia, but saboteurs, who see the road as a means of moving troops rapidly, sabotage his work. They raise up the locals, and Egawa is killed. Shirley Yamaguchi, who played Chinese characters in these Japanese-Chinese coproductions, makes a rousing speech and gets most of the villagers working. Work goes forward.
In the second half of this movie -- originally released in two parts -- Egawa's family dedicate themselves to completing his work. His younger brother, Kazuo Hasegawa. Comes to work on the road, followed by his love, whom he constantly rebuffs because of the danger. It all ends with a well-directed sequence in which heavy rains cause floods, and only incredible work by the peasants can save the road.
It's a pretty good example of engineers at work, facing all sorts of obstacles, but overcoming them by hard work and the occasional speechifying. The modern viewer will see a good deal of propaganda, with its anti-communist tone, and talk about Greater Asia. I've seen several of the Japanese movies from this era, and the agitprop is held to normative levels.
