Momotaro, the Peach Boy, is a cute character that is familiar to the Japanese and the story has been around since as long ago as the end of the 14th century! However, this nice tale was used as a propaganda tool through the 1930s and 40s in order to glamorize and legitimize Japan's wars with most of the countries around them as well as the United States and Britain. In one of the later Momotaro films, features Momotaro and his friends fighting against the dreaded Americans ("Momotaro, Sacred Sailors", 1945) and in "Sora no Momotaro" the film appears to be an allegory concerning the Japanese invasion of Manchuria.
In the original tale, Momotaro is born out of a giant peach that is discovered by an old Japanese couple. Soon the boy grows and sets out on an adventure to fight the evil Oni (sort of like demons). Along the way, he befriends a dog, a monkey and a pheasant and the four of them ultimately fight and defeat these foes.
In "Sora no Momotaro", some animals are being harassed by an evil eagle (representing America). Even though the war is thousands of miles away and is dangerous, the four fly on a dangerous mission to free the oppressed animals and capture the eagle.
The purpose of the film is to paint the Japanese invasion of Manchuria, China, is to justify it as a peacekeeping mission to help the oppressed locals. No matter that the locals weren't being oppressed AND 'helping' them including killing many, many, many Manchurians....but in the film it's anything like the reality of this war.
Normally I do NOT talk politics in my reviews, but it just isn't possible to talk about this one without explaining what the film means and why it was made. In this case, it was pretty insidious to take cute children's characters and use them to justify a war of aggression and, in many cases, extermination. But Momotaro was used many times for such purposes and I've seen three or four cartoons like this one.
Overall, not a great cartoon since it's all based on a lie, but also an interesting one for historical reasons. Odd but at least it was reasonably well animated.