I found out this fact only last year when I searched a bit for WW1 history when I was looking for old World War 1 pics online after seeing some Indian soldiers in Wonder Woman movie (thanks to Patty) , which is set around that period. This is a part of history that is often neglected for some reason, even in India. (speaking as an Indian here.)A look at some forgotten sacrifices in the West that's best seen in it's entirety here:
I myself was unaware of the over 1 million soldiers from British ruled India that served in WWI.