The ducks are at war with the frogs in the pond. The frogs steal their loaches, and have a big battleship, which they aim at the ducks on the hill.
All of which seemed pretty much standard from the twenty or so Japanese cartoons I have seen from the era, although the animals representing nations is different. Monkeys are the Chinese, usually. But not here. And, at the end, ducks and frogs shelter together against the storm.
So is this an outlier, something slipped past the censors by the cartoon maker, a lone pacifist cartoon among the many urging Japanese children to martial valor? Or one of several pacifist cartoons I have not seen because, well, I have not seen them?
I think not. In the midst of their war against China, Japanese authorities in the parts controlled by the Japanese were already producing movies aimed at the Japanese, often importing Japanese talent. These features had a clear propaganda message, against the Chinese nationalists, the communists, and worst of all, the perfidious Europeans. That;s what I think is going on here.
There's some nice animation work here, with a couple of amusing gags.