Japan's war in the Pacific began decades before the attack on the US fleet at Pearl Harbor. By the end of 1800, the Japanese had decided to expand their territory into Asia. Japanese officials said the move would help the country get the resources it needed, especially oil. Around the turn of the 20th century, Japan's desire to build a modern industrial civilization led it towards a policy of extension. At the end of July 1894, Japanese troops attacked Chinese forces posted on the Korean peninsula. Four days later, on August 1, 1894, Japan declared war on China.