Before the outbreak of the First World War, Japan had established control on several countries including Korea and Sothern Manchuria.  She had also attained a lot of economic property.  The tendency of capitalism was increasing in Japan and she was planning to establish her economic empire in China.

The First World War broke out in 1914 A.D.  Japan also wanted to take part in it.  So she threatened Germany on the issue of Sigtao and Shantung and declared war against Germany on 23rd August 1914 A.D.  Thus, he entered the war from the side of allied.  This war was being fought in the territory of China and she did not have powers to oppose it due to her weaknesses.  Soon Japan captured Sigtao and establish control on the German railways and mines in Shantung province.

After the end of war when Yuan Shi Kai informed Japan regarding neutrality of Chinese in the province of Shantung, Japan opposed it immediately and put her notorious twenty one demands before China.  The aim of these demands was to stop the entry of foreigners in China, therefore made slogan the Asia is for Asian which is also known as the Monroe Doctrine of \Asia.  In order to get her demands accepted Japan gave an ultimatum to China which terrified Yuan Shi Kai and he accepted most of the demands of Japan.  Thus Japan established her control over Shantung by the display and terror of military power.

Japan received several advantages in the First World War.  She did not participate in extensive field of war and confined herself only to Far East.  So she had not to face so much harm as her other allies had to sustain in the war.  Japan sold war material to the European country during war and earned a lot of money.  But this industrial development of Japan became a source of worry for England because Japan began to be known as the England of East in the field of industry.