Mahabharata (formed in the 5th or 4th century BC) and Ramayana (formed in the 4th or 3rd century BC to the end of the 2nd century BC) are both important historical documents to study the military development of kings and nations in ancient India. From this, we can know that the ancient Indian army has developed from two arms (chariots and feet) in the Vedic era to four arms: gait, chariots, riding and elephants. As for the establishment of armies in different countries, there are different records in historical books. According to the first chapter of Mahabharata, it is recorded as a three-thirds system with four arms, and its smallest unit "Poti" is equivalent to today's class, consisting of an elephant, a car, three horses and five soldiers; Sanbotibu 1 Senamok, Sansenamok 1 Molimo, SanMolimobu 1 Gona, Sangonabu 1 Wahini, Sanwahini 1 Plitner, and Sanplitner. Akshony is its largest unit, equivalent to a modern legion, with 656 1 elephant, 656 1 chariot, 19683 cavalry and 32805 infantry. The compilation recorded in the same epic "Preparing for War" and "Peace" is not only different from this, but also far from it. For example, the compilation in "Preparing for War" is: 500 chariots and 500 war elephants 1 Senna, 10 Senna 1 Plitner and 10 Plitner. At present, it is difficult to explain why there are these differences in preparation, probably because different countries have different preparations. These four arms are the traditional arms of ancient India. Even in the story of the Tang Dynasty in the 7th century, it was still said that "where there are four soldiers, there are steps, horses, chariots and elephants". Although the Peacock era added two arms, the navy and the trench, and became six arms, it was not a common phenomenon for a long time. After the Gupta Empire, chariots were gradually abandoned, leaving only three arms: feet, riders and elephants.