The main reason is that the folk customs of Qin are tough. With the encouragement of Shang Yang's political reform and military law, he will definitely kill the enemy, change his fate and increase his official position. In the eyes of Chi, the enemy's head is above, that is, land, houses, money and status. Seize one by one, get a corresponding number of land and houses, and become a military landlord. Moreover, titles symbolize social status. In Qin Jun, different titles have different food treatment. The higher the title, the better the food. Those who have no title can only eat coarse grains to fill their stomachs. So people will try to kill the enemy and change their destiny. Slaves can redeem themselves and become civilians by killing two heads in the army. In the past, slaves could not change their fate except the kindness of their masters. Now that they have this opportunity, they must work hard. Anyway, after a few hits, you may turn over and become a landlord.

Most soldiers from the other six countries joined the army to make a living.

This is the gap.