In January 1942, the United States War Production Board (WPB) began rationing food, gasoline and other resources deemed important to the war effort. In addition, many American factories converted to production of war materials.
In March 1942, the WPB issued an order prohibiting the production of toys that contained critical materials (iron, steel, zinc, and rayon) that made up more than 7% of their weight.
In compliance with the WPB order, toy manufacturers began producing items such as paper dolls, puzzles, board games and hobby sets with military themes. For example, the Lionel Corporation (famous for toy electric trains) produced a freight train made entirely out of heavy-duty paper stock.
Nikudan Sanyushi: Human Bullets, 3 Brave Warriors