Japan's Entry into the War
On August 25, 1914 Japan sent an ultimatum to Germany demanding that they handover the territory of Jiaozhou and without compensation and also that they withdraw their warships from Japanese and Chinese waters. When Germany refused to comply, Japan entered the war on the side of the Allies on August 23, 1914. In November 1914, Japan captures Qingdao, a German-held port in China's Shandong Province, and between August and November, they also gained control of the Marshall Islands, the Mariana Islands, Palau, the Carolines, Samoa, and New Guinea.
Gallipoli
To break the stalemate on the western front, Weston Churchill suggested that an Allied strike on the Ottomans would hurt the Germans. The British high command decided to land a combined force of English, Canadian, Australian, and New Zealand soldiers on the beaches of the Gallipoli peninsula. Turkish defenders quickly pinned down the Allied troops on the beaches. Allied forces quickly dug in and engaged in trench warfare. The battle produced a total of 250,000 casualties on each side.
United States Entry into the War
The United States entered the war because of two main reasons. The first was because the British intercepted a telegraph from Germany to Mexico saying that they would support a Mexican invasions on the United States. Secondly, German attacks on American ships persuaded America to join the war on the side of the Allies.
This newspaper article shows that Germany was the Untied States main rival in World War 1.