When Qin Shihuang unified the world, the soldiers of the six countries were not needed, so he collected all the weapons of the six countries and cast twelve gold men in Xianyang City. The regular troops of the imperial court are all Qin people, and they are usually stationed in Guanzhong. At the same time, the east and south lanes, that is, highways, were built. When things get into trouble, the army can quickly arrive to suppress them. Therefore, the military system in the early Qin Dynasty was a limited conscription system only for Qin people.

However, the unification of the world and the vastness of its territory are not comparable to those of the former vassal States, so in the thirty-third year of the first emperor, a letter was issued to recruit refugees, husbands and businessmen as pawns. Hundreds of years of war in the Spring and Autumn Period and the Warring States Period, the good people were tired of fighting and unwilling to be soldiers. The Qin Dynasty recruited vagrants and rogues as soldiers, and gradually lost the sense of honor as soldiers and became a humble profession. It was from the Qin Dynasty that soldiers and bandits were indistinguishable and soldiers and civilians hated each other.

The first emperor unified the six countries, and the soldiers of all countries were either killed by Qin Jun or killed by Qin Jun. Only Chu State preserved a certain strength, so Oracle Bone Inscriptions said at that time: "Although there are three households in Chu, Qin will die." Both Liu Bang and Xiang Yu are Chu people. With Zhang Han's 200,000 Qin Jun killed by Xiang Yu, the last organized and trained regular professional army in China perished, and the Qin Dynasty perished!

Qin Jun, the master of the tiger and the wolf, once frightened the six countries because of his bravery.

After Qin Shihuang unified the six countries, he took two major military actions, which basically hollowed out the national power.

One is to attack the Huns in the north. Meng Tian led 300,000 troops to the Great Wall, and Fu Su, the eldest son of Qin Shihuang, supervised the army in Shang County, which was the most elite army in the Qin Dynasty. After Fu Su and Meng Tian were killed by Zhao Gao and Li Si, the Great Wall Corps was replaced by Wang Li. After Meng Tian's death, the northern army was divided, and its fighting capacity was not as good as before.

Second, take Baiyue from the south, command Tu Youyou, Ren Tao, Zhao Tuo and others to lead a so-called 500,000-strong army, and divide the troops into five roads to attack Baiyue tribe, capture Baiyue, and set up three counties in Nanhai, Guilin and Xiang Jun. After the death of Sui and He, Zhao Tuo became king and established Nanyue State, which did not perish until the Western Han Dynasty.

The hinterland of the dynasty was empty, leaving only local troops to guard it. Most of the local troops are adherents of the six countries, with restoration ideas and people's hearts.

During the Guangwu Uprising, Chen Sheng and Qin Ershi did not use regular troops, but used Zhang Han to recruit 200,000 prisoners who built tombs in Lishan Mountain to form a temporary army to guard against the enemy. This untrained captive army actually defeated the peasant rebels, and finally Chen Sheng and Guangwu were defeated and killed. It can be seen that the military strength of the Qin Dynasty is not weak.

When the insurgents were surging everywhere, the Southern Legion established a separatist regime in Lingnan and held its ground. In the Northern Legion, Wang Li led 200,000 troops south, but was defeated by Xiang Yu in the Battle of Julu, and Wang Li was killed. Xiang Yu killed these Qin Jun soldiers and forced the rest of Zhang Han's army to surrender. 65,438,000 Qin Jun stationed in Wuguan surrendered to Liu Bang easily, and Liu Bang received 80,000. At this point, Qin Jun's main force was lost.