Japanese companies Toko and Nikko produced the largest number of large military binoculars during WWII. That is because while the United States of America and Great Britain developed radar in the 1930s and 1940s, Japan continued to focus on binoculars. They felt so secure in their superiority in the optics of binoculars, that they thought they wouldn’t need radar.
The first Japanese binoculars were manufactured by the Fujii Brothers in 1911: the Fujii Brothers Victor 8x20. The Fujii’s were excellent tradesmen whose business flourished since by the 1920s, Japan’s Navy had become the third biggest navy in the world. At first, they used optical glass from Germany, but when that became scarce during World War I, the Japanese government started making their own. As of 1918, Nippon Kogaku would design and produce the optical lenses in Japan. In between the two World Wars, production of photographic lenses also began in Japan. Tokyo Kogaku Kikay made these photographic lenses. In the time leading up to World War II, these Toko lenses became the standard for Naval Binoculars.
The Japanese navy equipped all their warships with naval binoculars, set on 90 feet high towers. The binoculars were huge instruments made of brass and steel. The lenses could see up to 20 miles away and were designed to catch as much light as possible. The main purpose of these Big Eye Naval Binoculars was to spot Allied ships during World War II, but they also searched for the enemy’s aerial positioning. These Japanese binoculars were indeed very powerful, so much so that the United States would take apart the binoculars from captured Japanese ships in order to reverse-engineer the Japanese technology and copy them for their own Navy. 
	
15x magnification
	
80mm objective lens diameter