In September 1940 Japan joined Germany and Italy in the Tripartite Pact, which divided Asia and Africa into spheres of influence. Japan's was to be Southeast Asia. As it became clear that war was ahead, Japanese military planners determined to develop precision optical equipment for range-finding, navigation, and bombing aids.
During World War II, when the U.S. military used electronics to track enemy ships and aircraft, the Japanese chose optics. Chiyoda Kogaku Seiko produced high-powered binoculars and other optical instruments with wartime uses. Demand was so high that it opened the Itami plant in 1942 solely to manufacture optical glass. In another document another company was Itami Glass Company and was founded under the IJN (Imperial Japanese Navy), they produced Binoculars and range finders.