This last classic Japanese cartoon clip from YouTube dates from 1944, and is an extract from an animated feature released in that year, called "Umi No Shinpen"("The Heavenly Sailors", as the clip's poster on YouTube, Dorataro, translated it).
Dorataro also states that, as most Japanese children had been evacuated from Japan's cities due to Allied bombing raids by the time "Umi No Shinpen" was released, it's pretty unlikely that many Japanese children saw it at that time.
Considering the widespread destruction of much of the Japanese film industry's facilities and product during World War Two, it amazes me that this, along with the various other pieces of classic Japanese animation that have posted here in the last few weeks, have survived at all.
Like you, am discovering these works for the first time, and I hope that you will enjoy them, and that they'll help give you something of a wider view of Japan and its popular culture, as well as of the 1930's and early '40's period of Japanese history, than you may have had before.
Be seeing you.