Part of the reason is that they were not fighting for India. The soldiers were all volunteers; soldiering was their profession, and they served the very British Empire that was oppressing their own people back home.
部分原因是他们并非在为印度作战。这些士兵都是志愿者；当兵是他们的职业，他们在为镇压本国民众的大英帝国作战。