What are the reasons why Indian soldiers work in the British and Indian armies?

In the process of conquering and ruling India, British colonists recruited an Indian mercenary, the so-called soldier "Paiyi". British colonists ruled 200 million Indian people with 240,000 Indian soldiers, and at the same time controlled these Indian soldiers with 40,000 British officers. Most Indian soldiers come from bankrupt farmers and craftsmen. They were forced by their livelihood and had to work in the army. There are serious racial discrimination and ethnic oppression in the British and Indian armies. The British regard Indian soldiers as lords in the army, and all senior officers are filled by them. Indians can only be promoted to captain. British officers arbitrarily detained their salaries, did not respect their national customs, and ordered Indian soldiers to shave their beards and remove caste marks, which seriously hurt the self-esteem of Indian soldiers.