World War I was marked by the February Revolution in Russia in 1917 and the entry of the United States into the war on April 6, and was divided into two phases. In the first phase of the Great War, although the Allies and the Allies

World War I was marked by the February Revolution in Russia in 1917 and the entry of the United States into the war on April 6, and was divided into two phases.

In the first stage of the Great War, although the contention between the Allies and the Allies was of the nature of a struggle for world hegemony and the expansion and consolidation of colonial empires, it was more directly manifested in the settlement of territorial disputes between European powers, such as the Alsace-Lorraine problem, and the independence and reorganization of the nation-states under the Habsburg monarchy. In this way, not only did the main battlefield of the war be in Europe, but the warring parties were basically European countries.

In the Allied camp, Germany, Austria-Hungary, bulgaria were traditional European countries, and Turkey also occupied a large area of land in the Balkans of Europe at this time. In the Allied camp, the countries that fought before April 1917 were not only Britain, France, Russia, and the unexpected, but also Portugal, Mende of Negoro, Serbia, Romania, San Marino, Japan, and Hejaz (part of the present-day Kingdom of Saudi Arabia).

Among these countries, with the exception of Japan and Hejaz, are "authentic" European countries. Hejaz was controlled by the Ottoman Empire before the War, and its influence and role in declaring war on the Allies in October 1916 after it was freed from Ottoman control with the help of the Allies. Although Japan rose to prominence as a regional power in the early 20th century, it was also an ally of Britain. But after entering the war, it was only to expand its interests in Asia, and did not intervene directly in the wars in Europe, nor did it provide it to the Allies