The battle of Midway was a decisive battle in the Campaign of the Pacific. It took place between June 4th and June 7th of 1942. The United States Navy managed to defeat the attacking fleet from the Japanese Empire, who sought to execute a rapid and surprise attack on the American ships, just like in Pearl Harbor which had happened 6 months before. However, erroneous Japanese assumptions led to a devastating defeat of the Japanese fleet at the hands of the US Navy. The outcome of the battle proved to be decisive in the rest of the war, as Japan could never fully recover from the losses.
Children used to work in factories due to child labor. The men would be off fighting in wars and the women would work at factories or stayed at home. With children they didn't have to get paid because of their age and were treated badly. That is why they were chosen to start working in factories.