The Indian army as we know it today was the British Indian army and traces it origin to the beginning of the days of the rule of the East India Company. In 1947, the prefix British was dropped and it became the Indian army, but in all aspects it remained as the British had left it. It was basically a higher caste army and was recruited on the basis of caste and religion. Thus the infantry regiments were all caste based. The lower castes and the untouchables were never recruited by the English. This was a continuation of the old Hindu caste system that forbade Shudras to muster arms on pain of death. The British accepted this Hindu concept, but brought in a few of their own.
The British divided the populace at large into martial and non-martial races. This distinction was made on the basis of their own experience in battle and also a study of the socio-economic history of India. The British were of the view that races who had faced perpetual wars were martial. Here they accepted the Hindu theory and division between Kshatriyas( Warriors) and non -kshatriyas.
The British were impressed by the fighting prowess of the Sikhs, Jats, Rajputs, Gurkhas, and Mahrattas and classified them as martial races. Of these the Sikhs, Punjabi Muslims and Gurkhas had pride of place because in battles with them the British had a tough time.
The British first tasted a tough challenge during the Anglo-Gurkha wars of 1815-15. The Gurkhas fought bravely and though defeated won the admiration of the British. Again in the Anglo-Sikh wars of 1846-49, the English would have been defeated, but for traitors in the ranks of the Sikhs. The Prime Minister and his general Labh Singh were in league with the East India Company and conspired to defeat the Sikh army. However at Mudki and Chillianwala, the British tasted defeat. The East India Company won the war, but their admiration for the Sikhs as a martial race was engraved in their mind and at any given time the Sikhs with a population of 2%, yet constituted 33% of the British Indian army.
The British also had a healthy respect for Punjabi Muslims and Pathans, which was a result of the 3 Anglo-Afghan wars, where the British were hard pressed. The British were convinced that the hardy tribes of the North West frontier were martial as they had been continuously facing invasion right from the time of Alexander the great, a period of 2000 years.
Were the British right in this differentiation of martial and non-martial races? The taste of the pudding lies in its eating and the British were proved right as the regiments of the British Indian army helped win 2 World Wars and also fought for the Raj from places as far as China and Singapore. How many know that the Boxer rebellion in Peking in China was subdued by Sikh and Punjabi troops of the British Indian army? Tibet was conquered by the Indian army in the famous expedition led by General YoungHusband.
In 1947, Pandit Jawaharlal Nehru and Gandhi decided that the caste-based regiments be retained. This was a practical step as these regiments had their own war cries and food and religious habits. Gandhi has gone on record so many times to say that he favored the Varna system of caste as it was the bedrock of Hindu society. He did not wish this caste system of the army, which was all higher castes be broken up. One cannot comment whether this was right or wrong as now more than 6 decades have passed and the caste-based recruitment continues.. Though the new regiments are broad-based, the core of the Infantry regiments remains as it was during the days of the Raj.