Begin of World War I June 1914
On 28 June 1914, Archduke Franz Ferdinand , the prince of Austria and the heir to the throne of Austria-Hungary, was assassinated by a Yugoslav nationalist and this triggered the First World War.
This was the immediate reason; the long term reasons were the imperialistic policies of the great powers of Europe viz. the German Empire, the Austro-Hungarian Empire, the Ottoman Empire, the Russian Empire, the British Empire, France, and Italy.
On the one side were the belligerents were such as France, British Empire, Russian Empire, United States, Italy, Japan, Belgium etc and on the other side were the central powers viz. German Empire, Austria-Hungary, Ottoman Empire and Bulgaria.
On 4 August 1914, England declared war against Germany. India naturally became a belligerent in the war. The Viceroy Lord Hardinge announced:
The war was none of our seeking, but it has been thrust upon us as a wicked and wanton manner…….
The British Government sought support of the Indians and most sections of the Indian society were with the empire. The moderates supported the war because, who knows their demands of self Government may be fulfilled after the war.