In the era of cold weapons, many people died in the war, but not many died directly in the battlefield, such as meat grinder. Thousands of people were killed, hundreds of people died, or thousands of people were killed. However, after the emergence of hot weapons and artillery, the efficiency of killing people was improved much more than that of cold weapons.
In the era of cold weapons, it would be difficult to wipe out 20000 people, if it was not a rout, and they might be invested in succession. Only in a considerable period of time can huge casualties occur..
But in front of hot weapons and machine guns, 20000 people are not familiar with the tactics of hot weapons, and of course they die