From Army of Empire: The Untold Story of the Indian Army in World War I, by George Morton-Jack (Basic Books, 2018), Kindle pp. 31-32, 36:
The men of the pre-First World War Indian Army were a tiny proportion of the Indian Empire’s population, just 0.07 per cent of 310 million. In July 1914 there were 217,000 volunteer Indian servicemen. Around 150,000 of them were active professional soldiers, 35,000 reservist soldiers and 32,000 non-combatants; altogether roughly two fifths were Muslims, nearly as many were Hindus, and a fifth were Sikhs. They were not remotely representative of India’s population as a whole. The combatant majority were members of an exclusive list of rural peasant farming communities to whom alone the British opened military service. These were the ‘martial races’, a mix of tribes, clans and castes mostly dotted about British India’s northern provinces–in the plains and hills of Punjab, the valleys of the North-West Frontier Province, and the southern slopes of the Himalayas in the United Provinces of Agra and Oudh–or beyond British Indian borders in the independent Pukhtun tribal areas or in Nepal. The British selected them in the pseudo-scientific delusion that their offspring were genetically fitter for fighting than India’s more numerous ‘non-martial races’. As George MacMunn, the pre-eminent British buff on the subject, explained: ‘In India we speak of the martial races as a thing apart because the mass of the people have neither martial aptitude nor physical courage, the courage that we should talk of colloquially as “guts”.’
A dearth of sources on individual Indian soldiers’ pre-war lives makes it difficult to fathom their personal motivations. But by generally following their journeys from their villages to the Indian Army between the 1890s and 1913, using snapshots from veteran interviews and also the viewpoints of British officers, it becomes clear that illiterate men of the martial races willingly joined up for a professional career with distinct benefits. The Indian Army for them was more than just an employer: it doubled as an educational institution that taught them many things, not least on overseas assignments prior to 1914. One British civil servant, as an administrator of numerous Punjabi martial race villages, judiciously summed it up with his nickname for the Indian Army: ‘the peasant’s university’.
Certain Hindu, Muslim or Sikh village communities tended to provide recruits for particular Indian regiments, so that companies could be filled with fathers, sons, brothers, uncles and cousins serving together, or at least with local men of the same faith. This was another vital attraction of soldiering: the regiment was a home from home. The regimental British officers did much to make the regiment a comfortable professional environment where village religious or community customs were respected. They doggedly studied their men’s languages, faiths and social ways, becoming quasi-anthropologists in order to ensure that the regimental kitchen turned out curries, dairy foods and other staples in keeping with company religious requirements; that daily prayers and annual holy festivals were accommodated in the regimental calendar; and that recruits were free to wear their hair as they liked according to their own community traditions, for example the Sikhs’ waist-length uncut locks tied up under the turban, or the Waziristani style of curls about the shoulders. They also strove to make military service consistent with tending to village matters, allowing men generous home leave.