World War I (also known as the First World War, Great War or War of Wars, abbreviated WWI) was a military conflict centered on Europe that began in the summer of 1914. The fighting ended in late 1918. This conflict involved all of the world's great powers, assembled in two opposing alliances: the Allies (centred around the Triple Entente) and the Central Powers.The Indian Army in fact outnumbered the British Army at the beginning of the war.
India under British rule contributed greatly to the British war effort by providing huge numbers of both men and resources.

World War II, or the Second World War[1] (often abbreviated as WWII or WW2), was a global military conflict lasting from 1939 to 1945, which involved most of the world's nations, including all of the great powers: eventually forming two opposing military alliances, the Allies and the Axis. It was the most widespread war in history, with more than 100 million military personnel mobilised. In a state of 'total war,' the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources. Marked by significant events involving the mass death of civilians, including the Holocaust and the only use of nuclear weapons in warfare, it was the deadliest conflict in modern human history..