The First World War was fought between allied nations and central powers. 

The First World War. began in 1914 C.E. The causes of the war were:

(i) Increase in production: Due to the industrial revolution machines came into use for the various production processes. It also led to increasing in production because of mechanization.

(ii) Imperialism: The European countries needed more raw material to match the quantitative increase in production and more markets to sell their surplus products. Imperialistic European nations began to search for newer lands to meet these needs.

(iii) Growing Militarisation: The search for newer lands and colonies would often create warlike situations among them. Keeping this in view more powerful nations in Europe felt the need to continuously increase their military power and armory.

(iv) Division of Europe into two hostile groups: Germany, England, Russia, France, Austria, Hungary where the nations of primary importance. Among them, rival groups were formed. Because of the rivalry, every nation began to enhance its military and naval strength, There was a competition to produce more and more destructive weapons.

(v) Immediate cause: The Austrian Prince Archduke Franz Ferdinand and his wife were assassinated by a Serbian maniac. In Austria, people believed that this whole act was maneuvered by the Serbian Kingdom. Hence, Austria called a war against Serbia. Russia came to help Serbia. Two distinct groups were formed, one group supporting Austria (Germany, Turkey, Bulgaria) known as central powers and another supporting Serbia (England, France, Russia) known as allied nations.