Japan Enters the War
On 15 August 1914, the Japanese government declared an ultimatum to Germany, demanding them to give them the territory of Jiaozhou (in northeastern China) without any compensation. It was said that they wanted to secure domination and enduring peace in Eastern Asia. When the Germans refused to hand over the land, the Japanese joined the allies on 23 August 1914.
Gallipoli
The British army felt that a good way to break down the stalemate would be to attack weaker member of the Central forces, the Ottomans, to hurt Germany. They tried to seize the approach to the Dardanelles Strait, in an attempt to open a water supply line to Russia through the Ottoman- controlled strait. The allies left the strait after their ships got damaged by floating mines. They then decided to begin an attack on the beaches of the Gallipoli peninsula. Turkish defenders did not allow that to happen, and allies got pinned on the beach where they began building trenches. This battle produced about 250,000 casualties.
United States Involvement
The United States became involved in the war after the sinking of Lusitania by Germany, which was carrying 128 passengers. It outraged the United States because they wished to continue trade with the warring countries, but Germany was interfering.