However, after World War I began, Japan began to develop gold and coal mining on a large-scale in Taiwan, for two main reasons. First, Japan at that point had the second-largest naval fleet in the world, requiring huge amounts of coal. In addition, Japan had to import most of its strategic materials, and in those days international trade was still gold-based, requiring gold to purchase products from abroad.
但歐戰開打後，當時日本的海軍艦隊規模居全世界第二，必須消耗大量的煤；此外，日本必須大量進口戰略物資，當時國際貿易還是金本位，也就是要用黃金向外國買東西，因此，日本在台灣大開金礦與煤礦。