* Germany: Germany was the main enemy of the United Kingdom during World War 1. The two countries had been rivals for decades, and the war was largely the result of Germany's desire to challenge the United Kingdom's dominance in Europe.
* Austria-Hungary: Austria-Hungary was Germany's ally during World War 1. The two countries had a close relationship, and Austria-Hungary was heavily dependent on Germany for military support.
* Ottoman Empire: The Ottoman Empire was another ally of Germany during World War 1. The Ottoman Empire was a declining power, but it still controlled a large amount of territory in the Middle East and North Africa.
* Bulgaria: Bulgaria joined the Central Powers in 1915. Bulgaria was motivated to join the war by the promise of territorial gains from Serbia and Romania.
Allies of the United Kingdom during World War 1:
* France: France was the United Kingdom's closest ally during World War 1. The two countries had a long history of cooperation, and they were determined to defeat Germany together.
* Russia: Russia was another important ally of the United Kingdom during World War 1. Russia was a powerful military power, and its involvement in the war helped to tie down German forces on the Eastern Front.
* Italy: Italy joined the Allies in 1915. Italy was motivated to join the war by the promise of territorial gains from Austria-Hungary.
* Japan: Japan joined the Allies in 1914. Japan was interested in expanding its influence in Asia, and the war provided an opportunity to do so.
* United States: The United States joined the Allies in 1917. The United States was a latecomer to the war, but its involvement was decisive. The United States provided the Allies with much-needed manpower and resources, and helped to turn the tide of the war in their favor.
Changes in alliances during World War 1:
* Italy: Italy initially declared neutrality in World War 1, but it joined the Allies in 1915. Italy was motivated to join the war by the promise of territorial gains from Austria-Hungary.
* Bulgaria: Bulgaria joined the Central Powers in 1915. Bulgaria was motivated to join the war by the promise of territorial gains from Serbia and Romania.
* United States: The United States initially declared neutrality in World War 1, but it joined the Allies in 1917. The United States was a latecomer to the war, but its involvement was decisive. The United States provided the Allies with much-needed manpower and resources, and helped to turn the tide of the war in their favor.