What does "See the dragon and remove its armor" mean? What is the origin and allusion

According to the Qin system and the Han system, ministers are strictly prohibited from carrying weapons when they meet the emperor. Otherwise, it will be a serious crime of rebellion.

Later it even extended to the protection aspect of _____ armor.

Actual combat armor cannot be worn when meeting the emperor and must be disarmed. The only exception is the decorative armor vest (such as the military ministers of the Tang Dynasty).

Seeing the Dragon Removes Armor is a movie starring Andy Lau. It depicts the story of Zhao Zilong who was loyal to the country and was seriously injured, but insisted on not removing his armor because the armor was covered with white linen clothes. Once the armor was removed, the injured blood soaked the clothes, and he was When the soldiers see it, their morale will be shaken.

That is to say, Zhao Zilong is facing a powerful enemy and is waiting for him. He will only disarm when he returns to the court, surrenders military power, and meets the emperor (see the dragon).