The success of a military system comes from it being able to muster strength in numbers, train and equip them appropriately. And all this depends on the economic system underneath.
A European feudal monarch might only have a few thousand men under his direct command, with the rest coming from levies from his vassals. This limits the amount of strength one person can hold on a battlefield, though the issue of lower-level leaders is already solved (this problem will always be present.) Compare this to nation-states being able to field massive armies under the control of one person.
In the same way, not being able to take advantage of all of the people in a society is a problem too. I am unsure to what effect caste inflected military participation. I doubt it was ever so strict as to prevent farmers from taking up arms. I'm unsure how many peasant rebellions happened in India, relative to other areas. China certainly had many. AFAIK, for much of Indian history there was more land than people to till it, so lords had to be careful to induce them to stay, lest they run away to better areas, with lower taxation and such.
A European feudal monarch might only have a few thousand men under his direct command, with the rest coming from levies from his vassals. This limits the amount of strength one person can hold on a battlefield, though the issue of lower-level leaders is already solved (this problem will always be present.) Compare this to nation-states being able to field massive armies under the control of one person.
In the same way, not being able to take advantage of all of the people in a society is a problem too. I am unsure to what effect caste inflected military participation. I doubt it was ever so strict as to prevent farmers from taking up arms. I'm unsure how many peasant rebellions happened in India, relative to other areas. China certainly had many. AFAIK, for much of Indian history there was more land than people to till it, so lords had to be careful to induce them to stay, lest they run away to better areas, with lower taxation and such.