Factory ships were not used by Japan until the 1930s. As whale catches diminished in coastal waters, Japan looked to Antarctica. Toyo Hogei K.K. purchased the Norwegian factory ship, Antarctic, renaming it the Tonan Maru in 1934. Refrigerator ships were sent along to freeze and transport the meat back to Japan. By capitalizing on both the meat and oil of whales, the Japanese industry continued to out-compete other whaling nations. Improvements in technology such as the world's first diesel-powered whale catcher, the Seki Maru, also increased the capacity to take whales. In the years building up to World War II, the Germans purchased whale oil from Japan and both nations used it in preparation for war.[44]
In 1937 London, the International Conference on Whaling, which Japan did not attend, led to additional limits on pelagic whaling in order to prevent excessive exploitation (and specifically the extinction of the blue whale) creating the International Agreement for the Regulation of Whaling. Regarding voluntary acceptance of restrictions: