Okay, so back in the olden days, there was a big war called World War II. It happened a long time ago, but it was a really big deal.
During the war, American soldiers had to go to other countries to fight. One of those countries was Japan. While they were there, some American soldiers met Japanese women and fell in love.
After the war was over, the soldiers had to go back home to America. But they didn't want to leave their Japanese girlfriends behind. So, they asked them to come to America with them and be their wives.
These Japanese women who married American soldiers are called Japanese war brides. It was a new and kind of strange thing for people in America at the time. Some people didn't like it, but other people thought it was really nice that the soldiers and their girlfriends could be together.
That's pretty much it! The Japanese war brides were just Japanese women who married American soldiers after World War II.