Answer:
Lack of materials
Explanation: Japan needed materials which was a majaor factor in why they invaded manchuria as a means to get much needed material to help Japan industrialize as Japan is not very rich in iron ore and other materials and as ww2 dragged on Japanese iron was described as iron sand because it was low quality and full of impurirties as the only way to keep a matrial carce Japan alive was to cut back on quality
