The most important thing for an ancient general to lead his troops to war was to give a speech to his soldiers, which was generally a vernacular to boost morale, and the time was not too long. The generals on the stage often just say a few words. The content of the speech is the same. It's nothing more than defending the country and promoting to a higher position. Only these words are most practical for soldiers.
In ancient times, few commanders spoke directly to hundreds of thousands of troops. After all, there are too many people to arrange, and there was no big tinker that could accommodate hundreds of thousands of people at one time in ancient times. Commanders generally speak only to soldiers or officers, and rarely speak directly to ordinary soldiers. Some ordinary soldiers have never even met the commander-in-chief, let alone had a chance to listen to him.
In addition, no matter which dynasty, the military department will select some loud and loud people from the soldiers to form a special command force. These people are responsible for recording the words of the commander-in-chief when he speaks, and then passing the meaning of the commander-in-chief to the ears of every soldier.
After the commander-in-chief's speech, there will be civil servants and scholars who will organize the commander-in-chief's words into notices, print them out and post them in the army. With so many means, soldiers are not afraid of not having a chance to understand what the commander said.
In addition to heralds, drums and military flags were used to convey orders in ancient times. These methods are easy to learn, and soldiers can easily understand their meanings.