Sri Aurobindo points out a major difference between our time and the time in which the teaching of the Gita took place. In our day and age, everyone is expected to carry all manner of duties. The individual is expected to be able to think and pray, fight and protect, undertake trade and commerce and interchange, and provide service, at various times of course, and in various ways.
In ancient India, however, it was recognized that individuals have different temperament, training and natural tendencies that suit them for one or another type of function, and the functions of society were thus stratified. One group was designated to govern, protect and, when necessary, do battle, and this was the Kshatriya, the warrior.
While it is true that in latter days, the inward psychological truth of this stratification was lost amidst an outer calcification and hardening, it should be remembered that we cannot judge a time past by current standards, but must find a way to understand the time in its own right. In the system that obtained at that time, only one class of people was expected to participate in warfare.
“The ancient Indian civilization laid peculiar stress on the individual nature, tendency, temperament and sought to determine by it the ethical type, function and place in the society. Nor did it consider man primarily as a social being or the fullness of his social existence as the highest ideal, but rather as a spiritual being in process of formation and development and his social life, ethical law, play of temperament and exercise of function as means and stages of spiritual formation. Thought and knowledge, war and government, production and distribution, labour and service were carefully differentiated functions of society, each assigned to those who were naturally called to it and providing the right means by which they could individually proceed towards their spiritual development and self-perfection.”
Sri Aurobindo, Essays on the Gita, First Series, Chapter 6, Man and the Battle of Life, pp. 45-46,