The Hindu religion has divided society on what is referred to as the caste system. The caste system is very rigid and lays down the social structure of society. Basically it means that the society is divided as per occupation into 4 distinct classes and its genesis is supposed to be the Rishi Manu. Manu gave some fanciful origin of the castes which can be dismissed as sheer fantasy.
Effect of the Caste System
However what we are concerned is the effect of this division of society on the military battlefield. Out of the 4 major castes, it was decreed that only one caste the Kshatriyas could bear arms. In particular the, Vaish and Shudras were forbidden to shoulder arms and weapons. This resulted in a large and significant part of the population being forbidden to handle weapons. They were also debarred from having any military training. The result of this fiat can be surmised from the fact that Hindus could never face their opponents in battle with their full strength.
Once an invader entered Hindustan the only force opposing him was the Kshatriyas. In case as it often happened the Kshatriyas were defeated or captured there was no second line of defense. Thus the basic principle of the art of war was conspicuously negated. The multitude of Shudras and Vaish having no military training and also forbidden to train in weaponry were just sitting ducks against the invaders.
In particular when the Hindus armies consisting mainly of Kshatriyas met the Moslems in battle they were effectively fighting with one arm tied to their back. The rigidity of the caste system militated against any plan of a unified defense. Once the Kshatriyas were defeated the Moslem armies had a field day and just advanced into India with no resistance worth the name. History records that the poor Shudras and unwarlike Vaish just accepted the inevitable as the Moslem armies advanced having routed the Kshatriyas.
Negation of Principles of War
The Kshatriyas had elements of bravery ingrained in them, but their knowledge of tactics, strategic planning and concentration of force as a principle of war was sadly lacking. They also negated a basic principle enunciated by Sun Tzu that offense is the best form of defense. The Kshatriyas rarely took the initiative, content to face the enemy at the gates of their castle or city. It is a pity as brought out by Field Marshal Montgomery in his History of Warfare that the Hindus displayed poor strategic sense as the passes of the North West, like the Khyber Pass were never guarded.
Now that the age of warfare of that period is over and the caste system blurred to an extant, it can be appreciated the disastrous affect it had on the conduct of war. No wonder the Hindus were repeatedly defeated by the Moslem invaders and ended up being a subjugated race in their own land to the Moslems. Maybe social scientists will like to study the effect of the caste system on the conduct of Hindu warfare.