The movie makes no conventional attempt to situate viewers at the outset. Instead we're plunged immediately into a series of images loosely organized around the theme of hard Spanish earth. However, the pastoral scenes soon give way to images of fighting men. But in the absence of explanation, viewers can't be sure if the soldiers are Republican or Falange (fascist). It's only after about 15-minutes, we find out these are people supporting the republic. Maybe Ivens or Hemingway is making a subtle point by withholding information, but the absence could be confusing to contemporary viewers.
The movie itself has some compelling images; however, I doubt that most go beyond generic war imagery of that time. One does, nonetheless, get a sense of the impact on the civilian population in the areas surrounding Madrid. In no sense is the film a survey of that bloody civil war as a whole. Instead, it's a narrow slice from the loyalist republican pov. But neither is the movie simply Stalinist agitprop, (the Soviets supported the elected government; Hitler and Mussolini the Falangist rebels; while the US and England remained neutral). Rather, a strong subtextual theme appears to liken support for the republic to bringing water to the dry Spanish earth, a not unreasonable pov.
It's also worth noting the anti-fascist side quickly became a cause-célèbre among artists and intellectuals disgusted by the US and England's refusal to aid a fellow democratic government. Thus the movie has a number of illustrious names attached to it. It's likely because of these names that I expected more than the overall result delivers. Nonetheless, the brief documentary remains a snapshot worth watching, even for those unfamiliar with the historical period.